Lone Druid
* 
Ghost Shroud can be use both offensively to slow Lone Druid or Defensively to prevent Lone Druid and The Spirit Bear from attacking him.
* 
Heartstopper aura burns the Spirit bear High HP over time. Additionally, it can deal decent damage to Lone Druid during his True Form.
Phoenix
* Phoenix constantly depletes its own health due to the health costs of its abilities. Unlike heroes that have a similar mechanic, Phoenix does not benefit from low health, nor does it really have a countermeasure for it. As such, Phoenix is a very vulnerable target for Necrophos to prey on, especially when caught off guard before it can cast 
Supernova.
Additional:
* Necrophos becomes a bigger threat the lower one's health gets, and unfortunately for Phoenix, most of its spells have noticeable health costs. Those costs, coupled with his Heartstopper Aura, means that staying in a teamfight for too long under Necrophos' presence will make Phoenix a more valid target for his ultimate, with its stun completely preventing any form of retaliation or protection. Necrophos players are also likely to buy more durability items such as 
Hood of Defiance, making him more able to withstand Phoenix's damage despite having no escape mechanisms.
* However, it is also important to remember that a Scepter-upgraded Supernova can help protect an ally from his ultimate.
Lone Druid
* Unless Lone Druid purchases a 
Black King Bar for his Spirit Bear, Ensnare will easily kite the Spirit Bear.
* Song of the Siren allows Naga Siren and her team to completely bypass the Spirit Bear and hunt for the Lone Druid himself when starting a fight.
* Lone Druid's lack of innate AoE capabilities mean that Naga Siren's illusions have no problem against him.
Phoenix
* 
Song of the Siren does not affect Supernova, which allows her and her team to focus the egg while the enemy team is affected by sleep.
* Phoenix cannot use 
Icarus Dive for escaping when rooted by 
Ensnare.
* However, Phoenix has many area-of-effect abilities that allow him to clear Naga Siren's illusions from 
Mirror Image.
Phoenix
* 
Sand King and 
Phoenix have many tools to deal with multiple enemies at once, which will work well against a crowd of illusions.
Lone Druid
* Chain Frost can deliver high amounts of damage to Lone Druid itself and his bear if they do not separate fast from each other.
Additional:
* 
Chain Frost will bounce between Lone Druid and his bear, forcing them to separate or suffer high amounts of damage.
Phoenix
* Phoenix does significant magic damage over time which can either be dispelled or negated by Fate's Edict.
* Oracle's burst damage potential can prove lethal to Phoenix, as they already have to sacrifice health to cast their basic skills.
Lone Druid
* 
Cold Embrace can protect allies from Lone Druid and the Spirit bear, who mainly deal physical damage
* 
Winter's Curse can turn Lone Druid and the Spirit Bear against his teammates.
Lone Druid
* Brewmaster can make the Spirit Bear a much smaller threat with Cinder Brew.
* Cyclone removes the bear from a fight so that his team can easily focus on the hero.
* While most heroes would be worn down by a Spirit Bear 
Radiance in the time it takes to kill Lone Druid, Brewmaster is protected in Primal Split.
Phoenix
* Earthbind can prevent Phoenix from using Icarus Dive, the only escaping mechanism of this hero.
* Heavy burst damage from Poof can easily kill Phoenix even when it slows down all the Meepos with 
Fire Spirits.
* Meepo's clones destroy the Phoenix Sun from Supernova in no time, even when they are slowed down by Fire Spirits.
* Meepo's naturally high magic resistance gives Phoenix a hard time with bursting him down. He can even turn the tide if Icarus Dive is on cooldown.
Additional:
* Meepo is unlike any other multi-unit enemy Phoenix may face in the battlefield. Unlike illusion-based heroes like 
Phantom Lancer or 
Chaos Knight, Meepo's clones are not illusions, meaning they can deal full damage to the Phoenix Sun if all four (or five) are present.
Lone Druid
* 
Arcane Orb deals heavy damage to both Lone Druid and the Spirit Bear.
* 
Astral Imprisonment can prevent the Spirit Bear from attacking, which is Lone Druid's main damage output.
* 
Sanity's Eclipse deals heavy damage to Lone Druid.
Phoenix
* Phoenix expends health to use its abilities, making it a good target for Thirst.
* Rupture deals heavy damage against Icarus Dive.
Additional:
* Although 
Blood Rite can be easily avoided, if it does hit, its lengthy silence and pure damage can be a severe punishment for a slow, unobservant, or simply unfortunate Phoenix.
* His 
Rupture can turn Icarus Dive into a suicide option, and it cannot be dispelled, meaning even if Phoenix completes a Supernova, choosing to Dive may just cut its health back down.
* And finally, due to Phoenix's health costs, too much careless ability spamming may just put Phoenix into Bloodseeker's vision through 
Thirst, making it a very tempting ganking target.
Phoenix
* Phoenix's limit AoE, damage-over-time abilities give Io plenty of time to save allies with Relocate.
Phoenix
* Spiked Carapace reacts on any of the damage over time from Phoenix's abilities and can interrupt 
Sun Ray and Icarus Dive.
Phoenix
* Ursa can easily unleash a number of attacks in an incredibly short amount of time, easily destroying the Supernova in a couple of seconds regardless of Fire Spirits' debuff. His 
Enrage also dampens any damage Phoenix might toss at his direction, as well as remove any debuffs Phoenix may place on him.
Phoenix
* Marci can destroy Supernova by herself with Unleash at any stage of the game.
* Phoenix is squishy hero with low armor and is very vulnerable for Rebound and Sidekick at the laning stage.
Phoenix
* 
Corrosive Skin gives Viper additional resistance to Phoenix's magical damage, and since they deal damage over time, Phoenix would be constantly afflicted by his passive's own debuff, making him not an ideal target for Phoenix's harassment. Phoenix's abilities also constantly drain its own health away, becoming more vulnerable to 
Poison Attack.
Lone Druid
* 
Firestorm's percentage damage can quickly demolish the Spirit Bear's high HP
* 
Pit of Malice will allow allies to easily kite Lone Druid due to his low mobility
Lone Druid
* 
Laser blinds Lone Druid, making his attacks miss.
Lone Druid
* 
Mystic Flare can be used to effectively ignore the Spirit Bear entirely and burst Lone Druid during the early mid game.
* 
Concussive Shot and 
Arcane Bolt will provide vision of Lone Druid allowing for better chase in teamfights before the Spirit Bear can do too much damage.
* 
Ancient Seal denies the ability to transform into 
True Form and receive bonus HP from the skill.
Phoenix
* Silence (and mana burns) will be a persistent problem for Phoenix, as it is heavily reliant on its abilities whether defensively or offensively, so heroes like 
Death Prophet, 
Skywrath Mage, and even 
Nyx Assassin must be closely observed to prevent being shut down by these heroes.
* Hexes are a greater threat to Phoenix as they also disable items, preventing Phoenix from dispelling the debuff on its own.
Lone Druid
* Skywrath Mage also has a terrible time fighting against anything that isn't a hero. His skills are mostly target-based and he has terrible strength and agility, he can easily be kited or harassed by illusion-based heroes like Chaos Knight and Phantom Lancer, or by Heroes that summon other units like 
Lone Druid, 
Lycan and 
Beastmaster.
Phoenix
* Anti-Mage dispels Phoenix's slows with 
Manta Style.
* Anti-Mage can Blink directly next to Supernova, giving him more time to destroy the egg.
Lone Druid
* Grimstroke's 
Soulbind will always reliably connect onto both of them if they are close together.
Lone Druid
* Dazzle easily breaks the position of Lone Druid and his 
Summon Spirit Bear with his 
Poison Touch, As it always hits from afar and prolongs the slowdown on the Summon Spirit Bear, which is why he cannot catch up with Dazzle and treat his master with 
Spirit Link
* Dazzle helps his team survive the physical attacks of the Summon Spirit Bear thanks to the treatment from 
Shadow Wave and armor from 
Bad Juju, which can enable his team to kill Lone Druid
* The Lone Druid Summon Spirit Bear has a small amount of armor at the start of the game, because of Mid Dazzle, it can very much break through it and prevent Lone Druid from gaining an advantage at the very beginning of the game, giving his team the opportunity to overtake Lone Druid on items for killing him, by type: 
Spirit Vessel
Additional:
* Dazzle easily breaks the position of Lone Druid and his Summon Spirit Bear with his Poison Touch, As it always hits from afar and prolongs the slowdown on the Summon Spirit Bear, which is why he cannot catch up with Dazzle and treat his master with Spirit Link
* Dazzle helps his team survive the physical attacks of the Summon Spirit Bear thanks to the treatment from Shadow Wave and armor from Bad Juju, which can enable his team to kill Lone Druid
* The Lone Druid Summon Spirit Bear has a small amount of armor at the start of the game, because of Mid Dazzle, it can very much break through it and prevent Lone Druid from gaining an advantage at the very beginning of the game, giving his team the opportunity to overtake Lone Druid on items for killing him, by type: Spirit Vessel
Phoenix
* As a hero with uncommon traits, Phoenix's abilities require more health than mana. It is advised for Rubick to purchase health regeneration items such as 
Tranquil Boots, 
Urn of Shadows or Hood of Defiance to keep up with the HP loss.
* Phoenix's signature Supernova, if casted successfully, can turn a teamfight around if being stolen.
* The initial lift and the following crowd control from the drop of 
Telekinesis can protect the egg from being attacked if casted right before Supernova with quick fingers.
* A successfully reborn Supernova refreshes the cooldown of Telekinesis as well as 
Fade Bolt, so don't hesitate to spam both of them before Supernova with the reasons mentioned above.
* Supernova has a stun range of 1200, which requires Rubick to have Level 3 
Arcane Supremacy at least to exceed its range. Consider buying 
Aether Lens or 
Blink Dagger to help with positioning.
* It is not possible to cast Supernova (as of 7.31c) with 
Aghanim's Shard's extra Sun Ray even with both spell stolen, since Sun Ray takes up two stolen ability slots.
* Icarus Dive is a useful repositioning ability for scouting, initiation or escaping.
* Fire Spirits aids with Rubick farming given enough HP regeneration. In early skirmishes, the stolen ability can slow the attack speed of the enemy team to a crawl.
* Combined with Fade Bolt, both the attack damage and attack speed of the enemy team are reduced if they have no source of dispel, effectively nullifying their physical attack damage.
* Sun Ray thrives in and after a teamfight by damaging enemy heroes and healing allies at the same time.
* Rubick can interrupt both Icarus Dive and Sun Ray by casting Telekinesis.
Phoenix
* Inner Beast helps Beastmaster's team destroy Supernova quickly.
Phoenix
* 
Lil' Shredder will make quick work of Supernova.
* 
Mortimer Kisses can easily hit a Phoenix using Sun Ray.
Phoenix
* Heroes that deal damage over time will also fail to bring down Abaddon and his allies, such as 
Huskar, 
Venomancer, or Phoenix.
Phoenix
* Heroes with spell immunity-granting spells will render Phoenix useless against them, as Phoenix has almost no spell immunity-piercing ability, other than the stun at the end of Supernova: 
Lifestealer, 
Juggernaut.
Phoenix
* Any hero with high attack speed will be a threat to Phoenix when it initiates, as they can easily tear down a Supernova, perhaps even while debuffed by Fire Spirits: Juggernaut, 
Clinkz, 
Troll Warlord, Beastmaster, 
Lina.
Phoenix
* Silence (and mana burns) will be a persistent problem for Phoenix, as it is heavily reliant on its abilities whether defensively or offensively, so heroes like Death Prophet, Skywrath Mage, and even Nyx Assassin must be closely observed to prevent being shut down by these heroes.
* Hexes are a greater threat to Phoenix as they also disable items, preventing Phoenix from dispelling the debuff on its own.
Lone Druid
* 
Pugna: 
Decrepify prevent the Spirit bear from attacking or protect allies from it.
Lone Druid
* Clinkz, 
Sniper, Lone Druid, Troll Warlord, 
Legion Commander and 
Wraith King are some of the Heroes that base themselves on attacks with little or no spell power, so they suffer in the grassy hands of Overgrowth.
Phoenix
* Any hero with high attack speed will be a threat to Phoenix when it initiates, as they can easily tear down a Supernova, perhaps even while debuffed by Fire Spirits: Juggernaut, Clinkz, Troll Warlord, Beastmaster, Lina.
Lone Druid
* 
Riki: 
Smoke Screen can prevent Lone Druid from using True Form and Savage Roar, additionally it cause the spirit bear to miss on attacks which reduce the chances of getting rooted from it, with diffusal Blade, he can keep Lone Druid or the Spirit Bear inside the Smoke.
Phoenix
* Any hero with high attack speed will be a threat to Phoenix when it initiates, as they can easily tear down a Supernova, perhaps even while debuffed by Fire Spirits: Juggernaut, Clinkz, Troll Warlord, Beastmaster, Lina.
Additional:
* Due to Fervor and Battle Trance, Troll Warlord is one of the best heroes to deal with Supernova.
Phoenix
* Heroes with blink or movement abilities, which are disabled by Pounce's leash: 
Anti-Mage, 
Earth Spirit, 
Faceless Void, 
Magnus, 
Mirana, 
Monkey King, 
Morphling, 
Pangolier, 
Phantom Assassin, Phoenix, 
Puck, 
Queen of Pain, Riki, Sand King, 
Spirit Breaker, 
Timbersaw, 
Tusk.
Lone Druid
* Timbersaw: Lone Druid will have a hard time dealing with Timbersaw due to his tankiness and high Armor from 
Reactive Armor
Lone Druid
* Heroes that have doubles or clones such as 
Arc Warden, 
Meepo or Lone Druid are vulnerable to Muerta's 
Gunslinger.
Phoenix
* 
Void can interrupt Icarus Dive.
* His 
Crippling Fear's silence will shutdown a spell caster Phoenix.
* However, Phoenix punishes Night Stalker with Supernova because it will turn night into day, and it has a higher priority than 
Dark Ascension, effectively canceling the passive bonuses Night Stalker gets from 
Hunter in the Night.
Phoenix
* Phoenix turns night to day, overriding Dark Ascension during Supernova.
Lone Druid
* Tiny can be a serious problem for the distance between Lone Druid and his Summon Spirit Bear with his 
Toss ability, since he will throw one away from the other, giving his team the opportunity to deal with either the Summon Spirit Bear or Lone Druid himself
* Lone Druid will not always be in his True Form, since she has her own recharge, which is why Tiny can find him with a 
Shadow Blade or Blink Dagger and kill him in a second with a combination of 
Avalanche and Toss, due to the fact that Lone Druid has a very small health reserve without True Form
Additional:
* Tiny can be a serious problem for the distance between Lone Druid and his Summon Spirit Bear with his Toss ability, since he will throw one away from the other, giving his team the opportunity to deal with either the Summon Spirit Bear or Lone Druid himself
* Lone Druid will not always be in his True Form, since she has her own recharge, which is why Tiny can find him with a Shadow Blade or Blink Dagger and kill him in a second with a combination of Avalanche and Toss, due to the fact that Lone Druid has a very small health reserve without True Form
Phoenix
* Heroes that are able to slow Tiny's attack speed, like Tusk and Phoenix, will greatly limit his Physical damage output.
Lone Druid
* Paralyzing Cask is likely to bounce between him and his bear every single time.
* Lone Druid's lack of mobility makes him vulnerable to Death Ward and Maledict.
Phoenix
* Heroes with slow movement speeds and small health pools (supports like 
Crystal Maiden or 
Witch Doctor) are easy targets for Phoenix. Should they be inflicted by its DOT debuffs, they will be very quickly killed without even getting a chance to fight back.
Lone Druid
* Morphling can ignore Spirit Bear and shorten the distance to Lone Druid with Waveform.
* Morphling can use his nukes to burst Lone Druid down, provided he is not rooted/disabled by Spirit Bear beforehand.
Lone Druid
* Heroes who just want to farm and avoid Lone Druid early will find it very hard to do so when he starts knocking on towers: 
Templar Assassin, Phantom Assassin, 
Ember Spirit, Morphling.
Lone Druid
* Reality Rift lets Chaos Knight bypass the Spirit Bear and jump onto Lone Druid.
* The Spirit Bear's lack of scaling means it dies quickly to Chaos Knight during the late-game.
Phoenix
* Heroes with strong area damage to destroy Phantasm illusions: 
Axe, Ember Spirit, Legion Commander, Phoenix
Lone Druid
* Lone Druid and The Spirit Bear cannot burst down Bristleback due to 
Bristleback
* Bristleback can easily run to Lone Druid without any hesitation, with 
Viscous Nasal Goo to reduce armor and slow the Spirit Bear or Lone Druid and 
Quill Spray can deal damage to both Lone Druid and the Spirit Bear at the same time
Phoenix
* Heroes with high health especially Strength heroes will take more damage on Sun Ray: Axe, 
Pudge, 
Bristleback, 
Mars.
Lone Druid
* Heroes who just want to farm and avoid Lone Druid early will find it very hard to do so when he starts knocking on towers: Templar Assassin, Phantom Assassin, Ember Spirit, Morphling.
Phoenix
* Her 
Refraction charges can and will be easily burned away by Phoenix's damage over time abilities, and 
Meld can't protect her from Phoenix's AoE abilities, even without detection.
Additional:
* Phoenix's abilities target and deals damage over time, making them a threat against Meld and Refraction. His abilities' nature makes them pretty hard to correctly land on the target, but that is not a problem against a Templar Assassin that needs to stand still during Meld.
* Icarus Dive allows Phoenix to shrug off the slow from her trap and make an easy escape from her ambush.
* As Templar Assassin relies on her quality-over-quantity bursting attacks to make quick work on fragile target, Fire Spirits' attack speed reduction can cripple her ability to deals any damage during combat. With the debuff applied in early-mid game, a Meld-breaking hit from her is significantly slowed to the point that her target can travel a safe distance before she even lands the hit.
* Sun Ray has a quick damage tick and will burn through her Refraction in no time.
* Supernova deals damage over time in an incredibly large area, and again with her quality-over-quantity style, she may not be able to attack quickly enough to break through the Phoenix Sun by herself. (not to mention the debuff from Fire Spirits) This can lead to a failed ganking attempt or even a turnaround.
Lone Druid
* Primal Beast is mostly played in the offlane role, so picking a carry who can escape from him is essential. Heroes such as Troll Warlord, Lone Druid and 
Outworld Destroyer, or generally any carry with a stun, slow or ability to fight back will stop him from having the good start he needs.
Phoenix
* Primal Beast is disarmed during Trample so will be unable to destroy a Supernova no matter how close it is to him.
* The same ability can also be used to save allies with the help of an 
Aghanim's Scepter.
* Sun Ray will do thousands of damage to Primal Beast if surviving a full channel time due to his high health scaling for the ability.
* Icarus Dive is a fantastic way to escape Primal Beast after he has used Onslaught.
* Phoenix has a naturally very high health pool making it hard for Primal Beast to deal with him with his magical damage.
Lone Druid
* Heroes who just want to farm and avoid Lone Druid early will find it very hard to do so when he starts knocking on towers: Templar Assassin, Phantom Assassin, Ember Spirit, Morphling.
Phoenix
* Fire Spirits applies a severe attack speed slow, severely hindering Phantom Assassin's damage output.
* Phantom Assassin cannot cast Phantom Strike on Phoenix during Supernova.
Additional:
* While her 
Phantom Strike does give limited extra attack speed, she cannot use the ability against the Phoenix Sun, and while her 
Blur may protect her from attacks, Phoenix's strong magical DPS burns away her small health pool quickly, and the attack speed slow makes her unable to fight back (provided she has no source of spell immunity).
Lone Druid
* Chaos Knight, Lone Druid, Meepo and Arc Warden can be hard targets since Shadow Demon's spells are ill-suited to fight many enemies at once.
Phoenix
* Icarus Dive quickly escapes from Shadow Demon abilities, especially 
Demonic Purge.
* Phoenix AoE abilities remove Shadow Demon's illusions created by 
Disruption.
Lone Druid
* Nukers who have set amounts of damage will really struggle against Lone Druid especially in True Form: Puck, 
Void Spirit, Mars.
Phoenix
* Heroes with high health especially Strength heroes will take more damage on Sun Ray: Axe, Pudge, Bristleback, Mars.
Lone Druid
* Lone Druid's early game is good against slow, squishy supports since his bear is very strong early game and an Entangling Claws proc almost always guarantees a kill: 
Ancient Apparition, Crystal Maiden, 
Shadow Shaman, etc.
Phoenix
* Heroes with slow movement speeds and small health pools (supports like Crystal Maiden or Witch Doctor) are easy targets for Phoenix. Should they be inflicted by its DOT debuffs, they will be very quickly killed without even getting a chance to fight back.
Phoenix
* Phoenix's large damage over time with Icarus Dive and Fire Spirits can kill Chen's allies before he can use Hand of God.
* Phoenix naturally buys Spirit Vessel, which allows him to reduce healing from 
Divine Favor and 
Hand of God.
* Phoenix's Supernova cannot be damaged by Chen's creeps, and their normal speed means they will often not be able to kill Phoenix whenever he uses Supernova.
Additional:
* Not only Phoenix is able to disrupt Chen's jungling with Fire Spirits, but its high damage over time can also force Chen to use Hand of God prematurely, potentially wasting any chance to save his allies during teamfights.
* Creeps' damage and attack speed are very abysmal, so Chen often cannot kill Phoenix whenever it casts Supernova.
Lone Druid
* Once caught in Bear's Entangle, Nature's Prophet cannot escape with 
Teleportation.
Phoenix
* Fire Spirits does damage over time, preventing Faceless Void from backtracking the full damage with Time Walk.
* Fire Spirits applies a big attack speed slow, stopping Faceless Void from doing many attacks while in Chronosphere.
* Sun Ray can heal allies and damage Faceless Void from outside Chronosphere.
* Supernova can be cast outside of Chronosphere, forcing Faceless Void to step away from it, lest he'll take a lot of damage
Phoenix
* Icarus Dive and Supernova can destroy the tree Monkey King is standing on.
* Fire Spirits reduces Monkey King's attack speed, preventing Monkey King from building up Jingu Mastery.
* Supernova can be casted next to Wukong's Command, forcing Monkey King to step away of it or to withstand its massive AOE damage
Additional:
* Icarus Dive, Sun Ray, and Supernova all destroy trees that Monkey King relies on to use his ability 
Tree Dance. If you spot him, you can quickly Icarus Dive in his direction and then follow up with Fire Spirits and Supernova. If you manage to cut the tree he is on, he will be stunned for 4 seconds and will be forced to take a lot of damage. However, most Monkey King players tend to build attack speed items to make use of their passive, 
Jingu Mastery, so a battle against a farmed Monkey King will depend on who gets the jump on the other first.
Phoenix
* Supernova negates Kunkka's combo entirely, as it can't be affected by spells while using Supernova.
* Icarus Dive also allows Phoenix to dodge Ghostship and Torrent.
Lone Druid
* Lone Druid becomes unkillable and impenetrable for Ember Spirit on the central line, as it has a huge reserve of health from the Summon Spirit Bear and a large regeneration from Spirit Link, which is why 
Sleight of Fist practically does not break through either one or the other on the line, and Lone Druid at this time can easily expel Ember Spirit from the line, push and gain gold and level
* 
Entangling Claws and 
Savage Roar abilities completely disable Ember Spirit's ability to dodge abilities or get out of an unpleasant fight for him on 
Fire Remnant, which can give the Lone Druid team the opportunity to kill him
Additional:
* Lone Druid becomes unkillable and impenetrable for Ember Spirit on the central line, as it has a huge reserve of health from the Summon Spirit Bear and a large regeneration from Spirit Link, which is why Sleight of Fist practically does not break through either one or the other on the line, and Lone Druid at this time can easily expel Ember Spirit from the line, push and gain gold and level
* Entangling Claws and Savage Roar abilities completely disable Ember Spirit's ability to dodge abilities or get out of an unpleasant fight for him on Fire Remnant, which can give the Lone Druid team the opportunity to kill him
Phoenix
* Phoenix will usually be on the sidelines or further back ready to use Sun Ray. Even after Magnus successfully uses Reverse Polarity and skewer Phoenix's teammates, Phoenix can usually counter-initiate using all of its abilities.
Phoenix
* Fire Spirits greatly reduces Slardar's already low starting attack speed (which Bash of the Deep relies on), making the laning phase very hard for him and discouraging Slardar from aggressively threatening lane kills.
* Supernova, ignoring Phoenix's lack of armor and Slardar's high damage single hits, is extremely hard for Slardar to take down on his own, especially after being hit by Fire Spirits.
* Icarus Dive is one of the longest distance escape spells in the game, and can help a good Phoenix escape from Slardar before he gets a Blink Dagger. However, the high cooldown means Phoenix is vulnerable to backstabs from any roamers after said spell is used.
* Slardar can interrupt an Icarus Dive from completing the flight with both of his stuns, however, likely leading to death if Supernova is on cooldown.
* A lot of the items a Phoenix builds throughout the game naturally counter Slardar. 
Shiva's Guard, 
Heaven's Halberd and 
Eul's Scepter of Divinity all stall Slardar's normal attacks in some way, while Spirit Vessel's percentage-based damage is good against his innate durability.
Lone Druid
* True Form gives Lone Druid a huge amount of health that no amount of 
Ball Lightning will chip through.
* Entangling Claws can mean a very quick end to the Storm Spirit as it prevents him from using Ball Lightning all together.
* Storm Spirit is a single target nuker, with the Shard Lone Druid can always fear him away from himself or the bear, defending the target he does not go on. This is assuming he cannot try and proc his entangle or a potential 
Skull Basher.
Lone Druid
* Lone Druid has a very large reserve of health against Invoker abilities, this allows him to survive a large number of attacks from Invoker and kill him, also Entangling Claws reveal invisibility from 
Ghost Walk, which allows the Lone Druid team to catch the popular QW-Invoker
Additional:
* Lone Druid has a very large reserve of health against Invoker abilities, this allows him to survive a large number of attacks from Invoker and kill him, also Entangling Claws reveal invisibility from Ghost Walk, which allows the Lone Druid team to catch the popular QW-Invoker
Phoenix
* Supernova allows Phoenix to save himself (or an ally, with Aghanim's Scepter) through 
Echo Slam. Earthshaker will also have a difficult time destroying the supernova, due to his low base attack time and poor agility.
* Icarus Dive can pass through Earthshaker's 
Fissure.
* Most of Phoenix's abilities disable Earthshaker's Blink Dagger for a good period of time due to the damage-over-time nature of its spells.
Phoenix
* Since all of Phoenix's abilities (except for Supernova) have health costs, heroes like Ancient Apparition or 
Necrophos can turn Phoenix's abilities against it. However, Supernova does completely protect Phoenix from 
Ice Blast.
Lone Druid
* Lone Druid's early game is good against slow, squishy supports since his bear is very strong early game and an Entangling Claws proc almost always guarantees a kill: Ancient Apparition, Crystal Maiden, Shadow Shaman, etc.
Phoenix
* Icarus Dive helps Phoenix escape from Cold Feet.
* However, all of Pheonix's basic abilities do cost health, which can be harmful under the effects of Ice Blast.
* Supernova can save Phoenix from Ice Blast.
Additional:
* Supernova with or without Aghanim's Scepter allows to save ally or himself through Ice Blast.
* Icarus Dive quickly escapes from 
Cold Feet.
Phoenix
* Sand King has nothing to deal with Supernova, as none of his spells are effective.
* The damage-over-time abilities of Phoenix disable Sand King's Blink Dagger very often.
Phoenix
* Due to Spirit Breaker's low attack speed, Supernova is problematic for Spirit Breaker to take down, and even more so with Fire Spirits debuff applied.
Lone Druid
* Savage Roar interrupts 
Starbreaker.
* Dawnbreaker is a slow moving hero. Although tanky, Lone Druid can eventually wear her down with his better movement speed.
Phoenix
* Sun Ray allows Phoenix to heal any allies caught in Berserker's Call while burning away Axe's high HP at the same time.
* Icarus Dive and Fire Spirits puts Axe's Blink Dagger on cooldown.
* Axe's slow attack speed makes it difficult for him to destroy Supernova on his own.
Phoenix
* Clockwerk being confined in his own Power Cogs means Clockwerk is unable to quickly escape from Phoenix's Sun Ray and Supernova.
* Sun Ray will also heal the enemy Clockwerk is fighting, making it unlikely for Clockwerk to take an enemy down with him.
* For the same reasons, Phoenix also makes a powerful ally for Clockwerk when the situation is reversed.
Phoenix
* Phoenix's Supernova cannot be damaged by Familiars.
* In the early and mid game, Sun Ray won't deal enough damage to be reduced by Gravekeeper's Cloak.
* Once Sun Ray deals enough damage to protect Visage, a layer of Gravekeeper's Cloak is burnt every 0.2 seconds.
Lone Druid
* Heroes who can fight back easily are not ideal matchups for Sven, such as Troll Warlord as mentioned above, Lone Druid and Templar Assassin.
Phoenix
* Heroes who depend on attacks (such as 
Shadow Fiend or 
Drow Ranger) can be nullified by Fire Spirits' attack speed slow.
Phoenix
* Heroes with high health especially Strength heroes will take more damage on Sun Ray: Axe, Pudge, Bristleback, Mars.
Phoenix
* Phoenix with Supernova
* Heroes that can dodge Glimpse:
* Puck with 
Phase Shift
* Riki with 
Tricks of the Trade
* Phantom Lancer with 
Doppelganger
* Ember Spirit with Sleight of Fist and 
Activate Fire Remnant
* Chaos Knight with 
Phantasm
* 
Naga Siren with Mirror Image
* Tusk with 
Snowball
* Juggernaut with 
Omnislash
* 
Brewmaster with 
Primal Split
* Lifestealer with 
Infest
* Phoenix with Supernova
Phoenix
* Heroes who depend on attacks (such as Shadow Fiend or Drow Ranger) can be nullified by Fire Spirits' attack speed slow.
Lone Druid
* Nukers who have set amounts of damage will really struggle against Lone Druid especially in True Form: Puck, Void Spirit, Mars.
Phoenix
* Heroes who can hide the Dueled target (Outworld Destroyer, 
Shadow Demon, Tusk, Phoenix with Aghanim's Scepter etc).
Additional:
* Legion Commander relies on her powerful attack and her 
Duel to be effective. But if Phoenix gets the jump on her first, she can find herself severely slowed, taking heavy damage, and find herself unable to Duel a burning Supernova.
* It must be noted that 
Press the Attack will both dispel the attack slow of Fire Spirits and grant her or whoever she targets bonus attack speed. This allows her to easily destroy a Supernova if caution is not taken to prevent this from occurring. As such, it would be a better decision to simply avoid a farmed or skilled Legion Commander instead of attempting to overpower her.
* If an ally is caught by Duel, Phoenix can use Sun Ray to heal the ally and damage Legion Commander, possibly swinging the Duel in their team's favor. Or with Aghanim's Scepter, Phoenix can save an ally from dying in Duel with Supernova and cancel the Duel as well.
Lone Druid
* Lone Druid's early game is good against slow, squishy supports since his bear is very strong early game and an Entangling Claws proc almost always guarantees a kill: Ancient Apparition, Crystal Maiden, Shadow Shaman, etc.
Lone Druid
* Besides Lone Druid and Meepo, Doom is potentially good versus every hero since Doom will render any hero helpless for up to 16 seconds. This is particularly true for fragile heroes that heavily rely on mobility to stay alive.
Lone Druid
* Lone Druid is essentially two heroes. Dooming one over the other still leaves Lone Druid or his bear able to do their job during a fight. Additionally, Lone Druid is not hindered as much as other heroes by the silence and mute of Doom since the hero relies more on attacks than abilities.
Additional:
* Doom will be very hestitant to use 
Doom on the Spirit Bear, and using it on Lone Druid himself will not stop the bear from attacking him especially if True Form has already been used.
* 
Devour does not work on the Spirit Bear and pushes the lane so Lone Druid can safely farm under tower.
Lone Druid
* Lone Druid and his Spirit Bear lack mobility, and are easy overwhelmed after being slowed by 
Diffusal Blade.
* Savage Roar is useless since Phantom Lancer can return to fight him again with his 
Phantom Rush.
Phoenix
* Phoenix's AoE abilities can prove troublesome for Phantom Lancer.
* Fire Spirits dramatically reduces Phantom Lancer and his illusions' attack speed.
* Icarus Dive's movement speed reduction makes retreating difficult.
* Supernova burns away illusions, and is invulnerable to attacks from illusions.
Lone Druid
* Illusions and summons are double-edge sword type of matchup for Luna. On one hand, they can tank damage from Eclipse, but on the other hand, she can easily clear them before Eclipse with Moon Glaives. Examples include 
Spectre, Shadow Demon, Phantom Lancer, Naga Siren, Chaos Knight, 
Terrorblade) or bring other units into the fight (such as 
Nature's Prophet, Lone Druid, 
Chen, 
Enchantress, Meepo and Arc Warden).
Lone Druid
* Heroes that create illusions: Spectre, Shadow Demon, Phantom Lancer, Naga Siren, Chaos Knight, Terrorblade) or bring other units into the fight (such as Nature's Prophet, Lone Druid, Chen, Enchantress, Meepo and Arc Warden) can cause Eclipse to strike the illusions/summons unintentionally. However, in many cases Moon Glaives can resolve this issue and eliminate them before activating Eclipse, but that will require lots of farming for right-click items.
Phoenix
* Although Phoenix has many ways to disable a Blink Dagger, the high cooldown of all of its spells makes them not as reliable for this. Also, its spells cost a lot of health to use, making it easy to get nuked down.
* Waning Rift prevents Phoenix from using Supernova to refresh itself, giving Puck's team time to finish it off, or allow Puck to burst Phoenix down.
* Dream Coil prevents Phoenix from using Icarus Dive without consequences. Waning Rift and Dream Coil are also able to cancel Sun Ray, which is its main source of damage in the late game.
Lone Druid
* Lone Druid has a huge reserve of health on the Summon Spirit Bear and a quick regeneration of his health with the help of Spirit Link, which makes the Puck's magical abilities useless, since they cannot break through such a large pool of health
* The ability of the Summon Spirit Bear and in the True Form of the Lone Druid Entangling Claws allows you to catch Puck when he released the 
Illusory Orb, since Puck will not be able to apply 
Ethereal Jaunt during the root action
Additional:
* Lone Druid has a huge reserve of health on the Summon Spirit Bear and a quick regeneration of his health with the help of Spirit Link, which makes Puck's magical abilities almost useless, since they cannot break through such a large pool of health.
* The ability of the Summon Spirit Bear and in the True Form of the Lone Druid, Entangling Claws, allows him to catch Puck when it releases the Illusory Orb, since Puck will not be able to apply Ethereal Jaunt during the root.
Phoenix
* Chemical Rage kills Phoenix very quickly in Supernova.
Lone Druid
* Alchemist likes to farm fast and be ahead, unfortunately Lone Druid likes to do the same by taking towers.
* 
Acid Spray will never prove a threat to Lone Druid or his Spirit Bear.
* 
Chemical Rage may not prove so useful once Lone Druid procs entangled keeping him in place.
* 
Monkey King Bar is a very good choice on Lone Druid's Spirit Bear and it directly counters any potential Radiance from Alchemist.
* 
Assault Cuirass is another very good Spirit Bear item that further makes Alchemist vulnerable to physical damage, which is all Lone Druid does.
* Alchemist is not the kind of hero who wants to go on single target summon units, by the time he has killed the Spirit Bear his teammates might had already been slayed by his teammates. Not to mention Lone Druid can just resummon it, even if he is successful.
Phoenix
* Tempest Double, Magnetic Field's attack speed bonus, and Arc Warden's high attack range will easily destroy a Phoenix using Supernova much faster than usual.
* Phoenix is very weak against pushers, especially those like Arc Warden who can kill him easily, as his skillset works best in teamfights.
Additional:
* His 
Tempest Double is not an illusion, but rather a full hero unit, which effectively reduces half of the Supernova's health. His 
Magnetic Field can tremendously boost his attack speed, allowing him to destroy Supernova in no time even when he's affected by Fire Spirits.
Lone Druid
* Because of his weak laning phase, Lone Druid absolutely overpowers him in the early to mid game. Lone Druid also directly counters most of his abilities.
* 
Flux is nullified when the Spirit Bear is nearby.
* 
Spark Wraith can get soaked by the bear.
* Lone Druid can easily go inside Magnetic Field and punish Zet.
Phoenix
* Heroes that depend on disrupting fights with ability combos or big ultimate abilities are vulnerable to the long stun of Fiend's Grip: 
Disruptor, Death Prophet, 
Enigma, Faceless Void, 
Invoker, 
Lich, Magnus, Mars, 
Medusa, Outworld Destroyer, Phoenix, Puck, Queen of Pain, Shadow Fiend, 
Treant Protector, 
Underlord, 
Winter Wyvern, Witch Doctor, 
Zeus.
Phoenix
* Heroes with hiding abilities can protect disabled allies: Outworld Destroyer, Shadow Demon, Tusk, Phoenix with Aghanim's Scepter.
Phoenix
* Silencer will most likely disrupt an initiation with his ultimate, 
Global Silence, prevent escape with his 
Last Word, and if Phoenix happens to die to him (or near him) enough times, he would sap enough of Phoenix's much needed Intelligence to make him a stronger foe and Phoenix with less mana than it already had.
Lone Druid
* Silencer's disables are useless on Lone Druid since he is more reliant on physical attacks rather than spells.
* Silencer has poor mobility so Lone Druid can run him down.
* Lone Druid's Shard will remove most of Silencer's spells once used.
Phoenix
* Juggernaut's high attack speed lets him destroy a Supernova easily. He can even attack a Supernova during Blade Fury with his regular attacks.
* 
Blade Fury protects Juggernaut from all of Phoenix's spells (except Supernova, which pierces spell immunity).
* Blade Fury can also dispel the attack speed slow from Fire Spirits and the movement speed slow from Icarus Dive.
* Phoenix's Icarus Dive will not protect it from Omnislash unless it dives into creeps, and Phoenix's low armor makes for an easy kill.
Lone Druid
* Omnislash spreads on both the bear and the druid, allowing them to survive.With enough levels,the bear can soak the ability alone and possibly dragging him to a dangerous location.
* Juggernaut cannot manfight the duo in the early game,because of their tankiness. If opposed in lane,Lone Druid can shut him down.
Lone Druid
* Huskar jumps on the hero without any problems, throwing the
Summon Spirit Bear away from him and forbidding him to beat, which knocks down the regeneration of Lone Druid from the 
Spirit Link ability, in addition, Huskar instantly deals fatal damage to Lone Druid, in some cases he does not even have time to squeeze the 
True Form
Summon Spirit Bear away from him and forbidding him to beat, which knocks down the regeneration of Lone Druid from the 
Spirit Link ability, in addition, Huskar instantly deals fatal damage to Lone Druid, in some cases he does not even have time to squeeze the 
True Form
Additional:
* Huskar jumps on the hero without any problems, throwing the
Phoenix
* Huskar's high attack speed can counteract
Fire Spirits, and easily destroy the 
Supernova.
Berserker's Blood will let Huskar easily face down a 
Supernova with increased attack speed.
Icarus Dive may not be an easy escape from Huskar either as he can chase Phoenix during it with 
Life Break if Huskar times it right.
Additional:
*
*
* However, Phoenix can buy items which can