* 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.

* Mana Drain has an fair long range and low cooldown. It can easily deplete most heroes of their entire mana pools, especially those with smaller mana pools such as Tiny or Spirit Breaker.

Additional:
* Lion can continuously Mana Drain Tiny in the early game, depleting his small mana pool for his abilities.

* Heroes with strong area-of-effect damaging and/or disabling abilities will be able to intercept Underlord and his team when they exit from Fiend's Gate: Luna's Aghanim's Scepter upgraded Eclipse, Dawnbreaker's Solar Guardian, Axe's Berserker's Call, Mars's Arena of Blood, Jakiro's Macropyre, Dual Breath and Ice Path, Naga Siren's Song of the Siren, Razor's Eye of the Storm and Plasma Field, Lina's Light Strike Array, Broodmother's Spinner's Snare from Aghanim's Scepter, Elder Titan's Earth Splitter and Echo Stomp, Alchemist's Unstable Concoction and Acid Spray, Queen of Pain's Sonic Wave, Dark Seer's Wall of Replica and Vacuum, Venomancer's Noxious Plague and Poison Nova from Aghanim's Scepter, Oracle's Fortune's End and Rain of Destiny from Aghanim's Shard, Bloodseeker's Blood Rite, Enigma's Black Hole and Midnight Pulse, Shadow Fiend's Requiem of Souls, Batrider's Aghanim's Scepter upgraded Flaming Lasso, Firefly, Flamebreak and Sticky Napalm, Ancient Apparition's Ice Blast, Sand King's Epicenter, Sand Storm and Burrowstrike, Gyrocopter's Call Down, Ember Spirit's Sleight of Fist, Death Prophet's Exorcism and Silence, Monkey King's Wukong's Command, Crystal Maiden's Freezing Field, Muerta's The Calling, Medusa's Stone Gaze, Zeus's Nimbus from Aghanim's Scepter. Dark Willow's Bramble Maze, Pangolier's Swashbuckle, Grimstroke's Soulbind, Ink Swell and Stroke of Fate, Earthshaker's Echo Slam and Fissure, Puck's Dream Coil and Waning Rift, Winter Wyvern's Winter's Curse, Magnus's Reverse Polarity.

* Ranged heroes that can easily harass Axe: Drow Ranger, Sniper, Lion.

* Illusion-based heroes are effective against Omnislash and Juggernaut's single-targeted damage: Naga Siren, Chaos Knight, Terrorblade,Phantom Lancer.

* Naga Siren with Mirror Image
* 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

* Due to her slow movement speed,heroes with crowd control and slows can shut down Dawnbreaker:Lion, Crystal Maiden ,Venomancer etc.

* Heroes with abilities or items that can silence or disable Anti-Mage for long periods of time will prevent him from Blinking away: Lion, Silencer, Shadow Shaman, Grimstroke, Witch Doctor, Riki, Faceless Void, Skywrath Mage, Puck.

* Backline supports (Lion,Crystal Maiden) can keep Puck pinned long enough for a kill.

* Heroes with high magical burst damage will kill Gyrocopter before he gets to do much: Lina, Lion, Zeus

* Sniper lacks any protection against Lion's disables early in the game.
* Lion's Earth Spike and Finger of Death may roughly hit Sniper at the latter increased attack range, making it possible to gank and to disable him from afar in clashes.
* Finger of Death is incredibly dangerous for Sniper as it may shred him away from fights, or in the worst scenario, cause his death.

* Ensnare with her attacks allows Naga Siren to gank Sniper easily.
* Rip Tide removes Sniper's very little armor.

* Heroes with channeling spells, for Chen has no disables on his own, hates buying disabling items and his creeps are often not fast enough to cancel them: Enigma's Black Hole, Witch Doctor's Death Ward, Shadow Shaman's Shackles, Lion's Mana Drain, Bane's Fiend's Grip, Pudge's Dismember, Crystal Maiden's Freezing Field, Pugna's Life Drain, Dawnbreaker's Solar Guardian, and Naga Siren's Reel In from Aghanim's Scepter.

* Naga Siren can make landing Chen's combo very hard due to her being an illusion hero thanks to Mirror Image.
* Rip Tide can deal big damage to Chen and reduce Chen's armor, as well as easily kill all of Chen's creeps.
* Naga Siren often builds Radiance, which allows her to quickly clear Chen's creeps.
* Ensnare will prevent Chen from escaping.
* With Aghanim's Scepter, Naga Siren can get access to Reel In, which can separate Chen from his creeps and draw him closer to Naga Siren and her team to finish her off. To make things worse, Chen has no way to cancel Reel In on his own, and must rely on outside from {U:Centaur Conqueror} or {U:Mud Golem} under his control.
* Carry or Nuker Naga Siren can often finish off Support Chen before he can have a chance to activate Hand of God.
Additional:
* Naga Siren can make landing Chen's combo very hard due to her being an illusion hero.
* Rip Tide can deal big damage to Chen and reduce Chen's armor, as well as easily kill all of Chen's creeps.
* Naga Siren often builds Radiance, which allows her to quickly clear Chen's creeps.
* Ensnare will prevent Chen from escaping.
* With Aghanim's Scepter, Naga Siren can get access to Reel In, which can separate Chen from his creeps and draw him closer to Naga Siren and her team to finish her off. To make things worse, Chen has no way to cancel Reel In on his own, and must rely on outside from {U:Centaur Conqueror} or {U:Mud Golem} under his control.
* Carry or Nuker Naga Siren can often finish off Support Chen before he can have a chance to activate Hand of God.

* Lion may upgrade Mana Drain, Hex and Finger of Death through Talent Tree and Aghanim's itens to make them affect secondary targets or turn them into AoE abilities. This can make things difficult for heroes like Phantom Lancer, Naga Siren and Terrorblade, who rely on illusion armies.

* Naga Siren can very easily dispel the Reflection with Mirror Image. And Besides Reflection that can be used to detect real Naga Siren, Terrorblade has no other ways to deal with Naga Siren's illusions. And what's worse is that Naga Siren can much easily detect the real Terrorblade due to Conjure Image having illusions having different colors. In addition, Terroblade is not a common Battle Fury nor Mjollnir wielder to counter this problem.
* Aghanim's Scepter upgraded Ensnare will allow Naga Siren to root Terrorblade even ithrough Black King Bar. And with Aghanim's Scepter, Naga Siren can get access to Reel In ability, which can allow her to pull Terrorblade toward herself and her team and away from his illusions, even through Black King Bar.
* Naga Siren can rapidly damage Terrorrblade and weaken Terrorblade's armor with Rip Tide, which combined with Terrorblade's low health and strength gain can almost completely discourage Terrorblade from even being present in teamfights. Rip Tide can also weaken armor of Terrorblade's illusions and damage them.
* Song of the Siren can be used to save an ally whom Terrorblade has used Sunder under the condition Naga Siren is quick enough to do it. And since Terrorblade has no "real" burst damage potential outside from Sunder, Naga Siren will usually have plenty of time to save an allied hero on which Sunder was used. Aghanim's Shard upgraded Song of the Siren can also heal her allies around her for it's duration, which allows Naga Siren to nullify effects of Sunder.
* However, Naga Siren's lack of burst damage can make it difficult for her to burst down Terrorblade before he can use Sunder unless Naga Siren has either Black King Bar or Linken's Sphere to protect herself against it or if she is played as Nuker.
Additional:
* Naga Siren can very easily dispel the Reflection with Mirror Image. And Besides Reflection that can be used to detect real Naga Siren, Terrorblade has no other ways to deal with Naga Siren's illusions. And what's worse is that Naga Siren can much easily detect the real Terrorblade due to Conjure Image having illusions having different colors. In addition, Terroblade is not a common Battle Fury nor Mjollnir wielder to counter this problem.
* Aghanim's Scepter upgraded Ensnare will allow Naga Siren to root Terrorblade even through Black King Bar. And with Aghanim's Scepter, Naga Siren can get access to Reel In ability, which can allow her to pull Terrorblade toward herself and her team and away from his illusions, even through Black King Bar.
* Naga Siren can rapidly damage Terrorrblade and weaken Terrorblade's armor with Rip Tide, which combined with Terrorblade's low health and strength gain can almost completely discourage Terrorblade from even being present in teamfights. Rip Tide can also weaken armor of Terrorblade's illusions and damage them.
* Song of the Siren can be used to save an ally whom Terrorblade has used Sunder under the condition Naga Siren is quick enough to do it. And since Terrorblade has no "real" burst damage potential outside from Sunder, Naga Siren will usually have plenty of time to save an allied hero on which Sunder was used. Aghanim's Shard upgraded Song of the Siren can also heal her allies around her for it's duration, which allows Naga Siren to nullify effects of Sunder.
* However, Naga Siren's lack of burst damage can make it difficult for her to burst down Terrorblade before he can use Sunder unless Naga Siren has either Black King Bar or Linken's Sphere to protect herself against it or if she is played as Nuker.

* Long range disables are really effective against dangerous area controllers and channeling Heroes, like Enigma, Faceless Void or Crystal Maiden, as it may cancel them or prevent enemies from doing further damage while keeping Lion in a relatively safe distance in the warzone.

* Mirror Image can dispel Frostbite. A similar effect can be achieved with Manta Style, a core item on Naga Siren.
* Song of the Siren can stop Freezing Field regardless of any kind of invisibility as well as allow Naga Siren's team to quickly close the gap on Crystal Maiden.
* With Aghanim's Scepter, Naga Siren can get access to Reel In ability, which can allow her to pull Crystal Maiden toward herself and her team and cancel Freezing Field even through Black King Bar.
Additional:
* Mirror Image can dispel Frostbite.
* Song of the Siren can stop Freezing Field regardless of any kind of invisibility as well as allow Naga Siren's team to quickly close the gap on Crystal Maiden.
* Ensnare allows Naga Siren and her team to quickly catch up with Crystal Maiden and kill her.
* With Aghanim's Scepter, Naga Siren can get access to Reel In ability , which can allow her to pull Crystal Maiden toward herself and her team and cancel Freezing Field even through Black King Bar.

* Heroes with high magical burst can easily kill Huskar when he is at low health: Lion, Lina, Skywrath Mage

* Mirror Image can cause Huskar to Life Break the wrong target.
* Rip Tide reduces Huskar's already low armor.
* Song of the Siren allows teams to recover from Huskar's initiation, as well as the damage over time from Burning Spears.

* Mana Drain depletes Necrophos's mana pool, preventing him from using his abilities.
* Finger of Death deals high magical damage, which becomes amplified by Ghost Shroud.

* Illusions make it difficult for Necrophos to target his Reaper's Scythe correctly, thus giving illusion heroes like Chaos Knight or Naga Siren an edge against Necrophos.

* Despite her high mobility, Hex or Earth Spike can lock Phantom Assassin down, make her vulnerable and mitigate her damage output.
* Lion relies entirely on his abilities to be effective, rendering Phatnom Assassin's high evasion through ineffective against him. And Phantom Assassin's low health pool makes her vulnerable to Lion's magical burst without Black King Bar.

* Ensnare prevents using any kind of movement abiilties, Making Naga Siren good against heroes who rely on gap-closing abilities to escape: Phantom Assassin, Magnus, Slark, Riki, Faceless Void, Storm Spirit.

* Heroes that can drain mana negatively affect Viper's ability to use Poison Attack, Nethertoxin and Viper Strike: Lion, Anti-Mage

* Naga Siren can easily disjoint, and dispel Corrosive Skin with Mirror Image.
* Since Viper is mostly a single-target hero, he will not have almost any chance against Naga Siren because she is an illusion based hero.
* Viper has no burst damage, so Naga Siren will have plenty of time to use Aghanim's Shard upgraded Song of the Siren heal her allies before Viper can finish them off.

* Wraith King has a very low mana pool and is extremely dependant on it to cast his high mana cost abilities, so Mana Drain will make him struggle way too hard, even not being able to active his passive ability Reincarnation, forcing the Wraith King to buy Aghanim's Shard as soon as possible.
* Althought Wraith King may not be as fragile to struggle against Lion's damage, it's much easier to disable and harass him, as Wraith King doesn't have any mobility at all, his only gap closer being Wraithfire Blast which costs too much mana for his mana pool, and may only affect one target.
Additional:
* While not being able to confront Wraith King by himself, Lion's Mana Drain helps in draining Wraith King's mana, preventing him from reincarnating unless he has his Aghanim's Shard.
* Lion's Earth Spike and Hex provide decent lockdown against Wraith King as well, preventing the latter from benefiting from Vampiric Spirit bonuses.

* Heroes with summons and illusions such as Broodmother and Naga Siren, are ill-suited for Wraith King to fight, as he has no source of waveclear.

* Heroes who can drain mana can make Omniknight useless after he uses one or two abilities: Lion, Anti-Mage, Nyx Assassin.

* Even though Naga Siren relies on direct attacks to deal damage for most of the time, Song of the Siren allows her to easily waste Guardian Angel.
* Ensnare fully works on targets affected with Heavenly Grace. However, Ensnare is dispellable with any dispel, and so can be dispelled by Heavenly Grace.
* As an agility hero that relies on illusions, Naga Siren is one of the most natural Diffusal Blade carriers, the bane of every hero with a small mana pool. Naga Siren can also buy items that deal magical damage like Radiance, Dagon, Ethereal Blade, Revenant's Brooch, Veil of Discord and Gleipnir to attack Omniknight's allies protected with Guardian Angel.
Additional:
* Although Naga Siren relies mostly on physical damage, Song of the Siren can be used to time out Guardian Angel, giving Naga Siren's team an easy opportunity to counter-initiate.
* Radiance allows it's owner to deal magical damage to multiple enemy heroes at once, and since Naga Siren often buys it, Guardian Angel is not a very good ability for protection against Naga Siren.
* Likewise, Nuker build Naga Siren (which primarly consists of items such as Radiance, Ethereal Blade, Dagon and Veil of Discord) can render Guardian Angel useless. Although Nuker is not a role Naga Siren should be playing.

* Heroes with forced movement abilities or non-interrupting forced movement, such as Lion, Drow Ranger, Magnus, Mars, as they can cancel blast-off mid air, removing his ability to initiate or escape.

* Heroes with summons like Broodmother, Enigma, Nature's Prophet; or illusions, like Naga Siren, Terrorblade are effective at keeping the choke points and rune spawns safe from Proximity Mines.

* Heroes with mana burn: Nyx Assassin, Invoker, Outworld Destroyer, Pugna, Lion

* Ensnare prevents using any kind of movement abiilties, Making Naga Siren good against heroes who rely on gap-closing abilities to escape: Phantom Assassin, Magnus, Slark, Riki, Faceless Void, Storm Spirit.

* Long range disables are really effective against dangerous area controllers and channeling Heroes, like Enigma, Faceless Void or Crystal Maiden, as it may cancel them or prevent enemies from doing further damage while keeping Lion in a relatively safe distance in the warzone.

* Ensnare prevents using any kind of movement abiilties, Making Naga Siren good against heroes who rely on gap-closing abilities to escape: Phantom Assassin, Magnus, Slark, Riki, Faceless Void, Storm Spirit.

* Hex abilities can cancel the channelling of Fiend's Grip : Lion, Shadow Shaman, Dazzle from Aghanim's Shard with upgraded Poison Touch.

* Heroes with illusions and summons can swarm and overwhelm Bane, who has no area abilities to deal with them outside from Aghanim's Shard upgraded Brain Sap: Broodmother, Chaos Knight, Naga Siren, Nature's Prophet, Phantom Lancer, Terrorblade, Visage, Warlock, Wraith King.

* Finger of Death can instantly shred many targets, especially fragile Heroes like Keeper of the Light, Ancient Apparition or Bounty Hunter.

* Naga Siren with Mirror Image
* Heroes that can remove the Track debuff with their skills:
* Abaddon with Aphotic Shield and Borrowed Time
* Huskar with Life Break
* Juggernaut with Blade Fury
* Legion Commander with Press the Attack
* Lifestealer with Rage and Infest
* Naga Siren with Mirror Image
* Omniknight with Heavenly Grace
* Oracle with Fortune's End and False Promise
* Phantom Lancer with Doppelganger
* Slark with Dark Pact
* Ursa with Enrage
* Weaver with Time Lapse
* Tidehunter with Kraken Shell when damage received reaches the threshold.

Additional:
* Bounty Hunter is a single target damage dealer, so he will not fare well against Naga Siren. Even though Bounty Hunter can use Track on her, Mirror Image will dispel the effect. Ensnare also reveals invisible units while they're rooted, putting Bounty Hunter at a disadvantage.

* Naga Siren is a natural split-pusher. With Rip Tide, she will easily out-push Nature's Prophet, farming his treants in the process.
* Ensnare prevents Teleportation. Even if he hides inside Sprout, Song of the Siren lasts long enough to prevent him from escaping.
Additional:
* Naga Siren is a natural split-pusher. With a Radiance equipped, she will easily keep the lanes pushed out, therefore keeping backdoor protection enabled and preventing Nature's Prophet from dealing building damage.
* Ensnare can prevent Teleportation. Aghanim's Scepter upgraded Ensnare can also affect Nature's Prophet even if he is spell immune. And Reel In from Aghanim's Scepter can also be used to separate Nature's Prophet from his treant and bring him close to Naga Siren and her team to burst him down.
* Song of the Siren will stop Nature's Prophet from escaping even if he has hidden inside of Sprout. Aghanim's Shard upgraded Song of the Siren can also heal her allies and save them from Nature's Prophet.

* Hex and Mana Drain can be used to immediately destroy Spectre's illusion when she Haunts. A fast fingered Lion can protect himself and a teammate.
* Hex and Earth Spike are good lockdown spells to control and kill Spectre, especially if she doesn't buy defensive items like Linken's Sphere and Black King Bar.
* Finger of Death can be used to burst down Spectre when she is low on life as she has very poor magic resistance.

* Lycan is a hero focused entirely on single target physical damage and lacks disables or AoE damage. Due to this, he will have difficulties dealing with illusions or Naga Siren's Ensnare.

* Drow Ranger has a very low health pool, allowing Lion to burst her down.
* Lack of any innate escape mechanism makes her an easy target for Lion's disables.
* Early on she can't deal as much damage to be life threatning. Her Gust is her best weapon against Lion.

* Hex's instant cast time will force Brewmaster into the awkward situation of needing some form of spell immunity or block to prevent being immediately hex upon blinking in, or wait until Lion has used all his crowd control before entering a fight. His direct magic burst also makes Brewmaster's Drunken Brawler worthless versus Lion.

* Weaver's exceptional ability to elude and survive through clashes and ganks is hard countered by Lion in every aspect.
* Weaver is very mana dependent and has a rather small mana pool in the beginning of the game, of which Mana Drain can deplete and lessen his early game presence.
* Earth Spike followed by Finger of Death in the huge majority of the time is enough to kill Weaver.
* Earth Spike can be point targeted to hit through Shukuchi.
* Hex's has a fair long duration, by which Weaver will not be able to deal damage, or even survive a coordinated attack, and it is single target, of which cannot be dodged.
* Mana Drain easily breaks Linken's Sphere. Its low cooldown allows Lion to infinitely break it whenever it recharges.
* Earth Spike and Hex when paired for the longer lengths of disables may diminish Time Lapse efficiency, possibly causing Weaver to not undo as much damage as he would.

* Ensnare and Song of the Siren can be used to cancel both, Tether and Relocate and to close the distance on Io.
* Rip Tide combined with illusions from Mirror Image often finish off Io before he can save himself with Tether or Relocate.
* Spirits's weak area-of-effect makes it a bad tool to deal with Naga Siren's illusions from Mirror Image.
* Once Naga Siren buys Aghanim's Scepter, she can gain access to Reel In, which not only allows her to cancel both, Tether and Relocate, but also to pull Io to herself and her team while he is affected with Ensnare, similarly to Batrider's Flaming Lasso.
* Aghanim's Shard upgraded Song of the Siren can also heal the hero Io and his Tethered targed try to gank.
Additional:
* Ensnare and Song of the Siren can be used to cancel both, Tether and Relocate and to close the distance on Io.
* Rip Tide combined with illusions from Mirror Image often finish off Io before he can save himself.
* Spirit's weak area-of-effect makes it a bad tool to deal with Naga Siren's illusions from Mirror Image.
* Once Naga Siren buys Aghanim's Scepter, she can gain access to Reel In, which not only allows her to cancel both, Tether and Relocate, but also to pull Io to herself and her team while he is affected with Ensnare, similarly to Batrider's Flaming Lasso.
* Aghanim's Shard upgraded Song of the Siren can also heal the hero Io and his tethered targed try to gank.

* Lion's instant cast point shuts down his initiation and buys time for his allies to catch up.
* Void Spirit has to be cautious when fighting, as he has no protection against Finger of Death. If caught out in a stun, the high magic damage could end him quickly.

* All of Lion's abilities are active making Demonic Purge break from Aghanim's Scepter useless.
* Hex and Mana Drain can make quick work of whatever illusions you're creating, especially when he acquires his Talents at level 20 and 25.
* An attempt to save an ally using Disruption can easily become a perfect setup for a Earth Spike or Finger of Death with Aghanim's Scepter for the enemy.

* Hex and Earth Spike can hold Clinkz down, giving him no chance to use Black King Bar or Skeleton Walk.
* Finger of Death quickly kills Clinkz due to his low health.

* 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.

* Lion has two low cast point disables (Hex and Earth Spike) to control Ursa before he buys a Black King Bar.
* Hex is one of the few abilities that cannot be dispelled even with an Aghanim's Scepter upgraded Enrage.
* Lion can control Ursa's low mana pool via Mana Drain.

* Naga Siren's illusions from Mirror Image can depush the lanes pushed by the Tempest Double, relieving the pressure.
* Mirror Image can dispel Flux, and the illusions can stop Flux from working to it's full power.
Additional:
* Song of the Siren stops Arc Warden from acting and allows Naga Siren's team to close in on him, past his Magnetic Field.
* Mirror Image dispels Flux. The illusions created from it also disable the slow from Flux if Arc Warden casts it after Mirror Image.
* Arc Warden's playstyle heavily favors split-pushing, which Naga Siren can compete against with her illusions.

* Lion may upgrade Mana Drain, Hex and Finger of Death through Talent Tree and Aghanim's itens to make them affect secondary targets or turn them into AoE abilities. This can make things difficult for heroes like Phantom Lancer, Naga Siren and Terrorblade, who rely on illusion armies.

* Heroes with nukes: Bane, Lich, Lion, Skywrath Mage

Additional:
* Enchantress is very fragile without any form of magic resistance, allowing Lion to easily burst her down.
* Nature's Attendants is a slow heal, making not as much effective against Lion's burst as it could be.
* Her raw movement speed is a fair escape/mobility mechanism, which may allow her to avoid a blindly cast Earth Spike, but does nothing against the rest of Lion's abilities, since they are single target and can't miss.
* Since Lion's damage comes mostly from his skills, Untouchable does nothing to mitigate it.

* Lion's Mana Drain is a headache for Bristleback to deal with during the laning stage, as it denies him the ability to get last hits with Quill Spray.

* Heroes with high burst damage through their physical attacks or spells can kill Dazzle or his allies before he has a chance to use Shallow Grave. (Lina, Lion, etc.)

* Mirror Image's illusions can easily walk straight at Dazzle and attack him, due to Dazzle's lack of reliable AoE nukes or disables.
* Ensnare roots Dazzle or his allies, making it harder to stay in range of Dazzle's saving abilities.
* Song of the Siren can be used to initiate a fight with superior positioning, potentially zoning Dazzle's high-impact spells out of the fight.

* Illusion-based and multi-unit heroes can take advantage of Chaos Knight's lack of area damage: Naga Siren, Phantom Lancer, Broodmother

* Illusion heroes like the aforementioned Phantom Lancer or Naga Siren, or heroes that tend to buy Manta Style, like Luna or Juggernaut, will give Slardar a hard time, as his damage is single-targeted.

* Heroes with high burst damage: Lina, Lion, Luna, Nyx Assassin, Queen of Pain.

* High priority targets like Queen of Pain, Drow Ranger, Ember Spirit can't get caught out from Lion's long range disables, making it harder to them fulfill their roles, and making it easy to target them.

* Ensnare prevents using any kind of movement abiilties, Making Naga Siren good against heroes who rely on gap-closing abilities to escape: Phantom Assassin, Magnus, Slark, Riki, Faceless Void, Storm Spirit.

* Nyx Assassin's skillset is mostly single-targeted, therefore he will have difficulties against heroes with illusions and summons: Naga Siren, Broodmother, Lycan, Visage, Phantom Lancer. And to make things worse, Nyx Asassin is not a common Battle Fury, Maelstrom, Mjollnir, Gleipnir or Radiance wielder to counter this problem.

* Mana Drain has an fair long range and low cooldown. It can easily deplete most heroes of their entire mana pools, especially those with smaller mana pools such as Tiny or Spirit Breaker.

* Heroes with summons and illusions as Spirit Breaker has no strong AoE capabilities to deal with them: Chaos Knight, Phantom Lancer, Terrorblade, Naga Siren, Broodmother, Warlock, Visage, Nature's Prophet, Shadow Shaman, Lycan, Wraith King.

* Heroes with silence and mana drain abilites, as Ancient Apparition relies entirely on his abilities: Invoker, Silencer, Nyx Assassin, Skywrath Mage, Shadow Shaman, Lion and etc.

* Heroes that can kill Death Prophet with nukes can prevent her from using Exorcism to its full duration or using it at all: Lina, Lion, Puck, Morphling.

* Skywrath's pitiful defences also make him easy meat to heroes with high burst like Juggernaut, Lion, or Phantom Assassin, the latter occasionally downing a support Skywrath in a single Stifling Dagger.

* Heroes that can keep Marci for a long time in one place so she can't pursue her targets, like Bane, Lion, Shadow Shaman, Invoker, Disruptor and Kunkka.

* Medusa lacks mobility or escape mechanisms. Earth Spike and Hex can neutralize her strong damage potential and allow for Lion's team to focus her down.
* Mana Drain is a perfect ability to weaken Medusa's durability as it can quickly drain her Mana Shield, making her far less tanky. Mana Drain can also be used to restore mana of Lion's allies, which can nullify the mana steal from Mystic Snake.
* Mana Drain, along with Hex, destroy illusions instantly, which may be extremely helpfull and efficient against core builders of Manta Style, like Medusa herself.

* Heroes that build Diffusal Blade or can fit it well into their item build will also make Medusa much less tanky: Riki, Naga Siren, Terrorblade, Juggernaut, Spectre, Slark.

* Ensnare disables Templar Assassin's invisibility and Blink Dagger (a core item on Templar Assassin), and her illusions will break Refraction easily.

* 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.

* If Meepo ganks Lion with Poof and Earthbind, he will be an easy target for Earth Spike & AoE Hex from his level 25 talent.

* Heroes with long or multiple disables will prevent Legion Commander from winning Duels: Shadow Shaman, Lion

* Song of the Siren lasts long enough to prevent a successful Duel (but only if Naga wasn't the target).

* Lion possesses two strong disables in Earth Spike and Hex and heavy magic burst with Finger of Death which help lock him down and prevent him from escaping with Activate Fire Remnant. When getting his Blink Dagger Lion can punish Ember Spirit's overextension immediately, or initiate a fight on him with disables.

* Mirror Image can be effective since Night Stalker cannot withstand fighting illusions. If he's unable to tell which Naga Siren is real, he will have a hard time landing his Void. However, if Night Stalker obtains an Aghanim's Scepter, the upgraded Void will hit and may even locate the real Naga Siren in fights.
Additional:
* Ensnare and Song of the Siren prevents Night Stalker from escaping and ganking during daytime or even nighttime.
* Rip Tide reduces Night Stalker's armor, making him easier to focus down.
* Mirror Image can be effective against Night Stalker, due to his single target abilities.

* With a lot of disables with good range, he might cancel your Echo Stomp.
* Mana Drain can be used to drain Elder Titan's already low mana pool.

* Song of the Siren completely wastes Abaddon Borrowed Time while keeping him in place.
* Naga Siren is able to simply dispel Abaddon's Curse of Avernus with Mirror Image before getting hit 4 times consecutively.
* Although Naga Siren's illusions can be easily destroyed by Aphotic Shield, Naga Siren can resolve that issue easily by purchasing Heart of Tarrasque to drastically increase her durability. Plus, the said item makes Naga Siren harder to be distinguished from her illusions.

* Heroes with heavy magical nukes will take advantage of Slark's poor HP or force him to use Shadow Dance early: Lina, Lion, Zeus

* Ensnare prevents using any kind of movement abiilties, Making Naga Siren good against heroes who rely on gap-closing abilities to escape: Phantom Assassin, Magnus, Slark, Riki, Faceless Void, Storm Spirit.

* Mana Drain rapidly saps Morphling's already low mana pool, making him unable to use Waveform or Adaptive Strike. Additionally, Hex prevents these abilities as well.
* An Earth Spike and Finger of Death combo can burst an unwary Morphling down if he has his strength fully shifted to agility.

* Any long duration disables that can pierce through both, Pierce The Veil and Black King Bar are devastating against Muerta: Enigma's Black Hole, Dawnbreaker's Solar Guardian, Axe's Berserker's Call, Naga Siren's Aghanim's Scepter upgraded Ensnare and Reel In from Aghanim's Scepter, Jakiro's Aghanim's Scepter upgraded Macropyre, Bane's Fiend's Grip, Pudge's Dismember, Batrider's Flaming Lasso, Beastmaster's Primal Roar, Grimstroke's Soulbind, Medusa's Stone Gaze, Magnus's Reverse Polarity.

* Heroes with powerful rooting abilities will disable most of Pangolier's skills, a bonus point if it pierces spell immunity since it will also be able to stop Pangolier during his Rolling Thunder: Treant Protector, Meepo, Crystal Maiden, Dark Willow, Underlord, Naga Siren

* Heroes with silences and hard stuns such as Doom, Silencer, and Lion can keep Mirana from Leaping away.

* Any hero who can counter-initiate in anticipation without getting caught in Reverse Polarity: Sven, Omniknight, Enigma, Luna, Naga Siren, Mars, Jakiro, Venomancer, Elder Titan, Faceless Void, Rubick, Keeper of the Light, Pugna, Invoker, Spectre, Alchemist, Treant Protector, Lina, Oracle, Zeus, Shadow Shaman, Phoenix, Razor, Huskar, Batrider, Kunkka, Tidehunter, Wraith King, Sand King, Medusa, Dawnbreaker.

* Finger of Death can instantly shred many targets, especially fragile Heroes like Keeper of the Light, Ancient Apparition or Bounty Hunter.

* Song of the Siren is very difficult for Rubick to Spell Steal when he is affected by sleep.
* Ensnare and Rip Tide together with some attacks can take Rubick down quickly, due to his low health pool and armor.
* Naga Siren usually buys Diffusal Blade, which may prevent Rubick from using his abilities.
* Mirror Image allows Naga Siren to dodge the incoming stun from Telekinesis (when she is not a target), and it can also dispel Fade Bolt's damage reduction debuff.

* Hex greatly reduces Timbersaw's mobility.
* In addition, Lion can follow up with his Earth Spike and Mana Drain combo, preventing Timbersaw to escape with Timber Chain. And he can finish Timbersaw off with Finger of Death if the latter's HP is low enough.

* Like above, supports with reliable stuns can be a massive problem and force Black King Bar in fights unideally, such as Shadow Shaman, Lion, Nyx Assassin.

* Since Windranger is bad against magical damage, heroes with continuous magical damage or magical nukes can blast her: Zeus, Tinker, Leshrac, Viper, Skywrath Mage, Lion, Lina, Venomancer.

* Enigma is fragile, and lacks escapes, being dependent on Blink Dagger for mobility. Ganking Heroes or Heroes with burst damage will likely kill him before he can do anything. Such Heroes include: Lina, Lion, Luna, Puck, Slark, Nyx Assassin, etc.

* Heroes with illusions: Chaos Knight, Naga Siren, Phantom Lancer, Terrorblade

* Sven is very vulnerable to chain stun such as Lion, Shadow Shaman or Magnus.

* Heroes with long disables, like Lion, Night Stalker, or Legion Commander, can prevent Oracle from using spells or items.

* Illusion heroes, such as Naga Siren, Phantom Lancer, Chaos Knight, Terrorblade will become strong against Tinker in the late game. Without Aghanim's Scepter Tinker is forced to defensively disarm heroes with Laser, leaving illusions free to deal physical damage which Tinker's low armor makes highly effective. In addition, Mjollnir or Battle Fury, two common pickups against illusion heroes, don't work well on Tinker at all.