Dark Seer
* Heroes with fast movement abilities will suffer huge damage when afflicted by Rupture: 
Spirit Breaker, 
Earth Spirit, 
Dark Seer.
Additional:
* 
Rupture can deal a lot of damage to either a surged Dark Seer or his allies and prevent the target from getting into position.
Keeper of the Light
* 
Blood Rite makes Ezalor chose between getting off Illuminate or getting silenced for a while, as Illuminate is a channeled ability.
* Blood Rite's silence can completely take Ezalor out of a teamfight, as he relies on his abilities to be useful.
* Keeper of the Light's only mobility source, his high movement speed (via his high base movement speed and through spirit form), is entirely countered by Rupture.
Dark Seer
* Dark Seer's strength lies in his high-mana cost skills. So 
Mana Break can be a great nuisance for him, since it can reduce his mana and prevent him from casting his spells.
* 
Mana Void can deal a lot of damage if Dark Seer spent a lot of mana on his abilities.
Keeper of the Light
* Being an intelligence caster hero, Ezalor usually has a high mana pool and low health and armor, making him a prime target for Mana Void
* Ezalor's Illuminate damage and Solar Bind's magic resistance reduction are greatly reduced thanks to 
Counterspell. Counterspell can also block and reflect Solar Bind if timed properly.
* Anti-Mage usually is not hampered by Solar Bind or Will-O-Wisp thanks to 
Blink.
* However, despite all of this, if Keeper of the Light is played carefully and tops off his team's mana at all times, Anti Mage will not be able to get off a good Mana Void.
* By the same token once Keeper of the Light gets a 
Octarine Core, he can spam Charka Magic to keep his own mana ful
Keeper of the Light
* 
Keeper of the Light can stall pushes with 
Illuminate. This makes him strong against pushing heroes: 
Terrorblade 
Naga siren 
Nature's Prophet and 
Anti-Mage
Dark Seer
* Dark Seer's only disable is Vacuum. Though he starts off with high armor and health, he'll eventually have a hard time dealing with high mobility heroes such as 
Weaver or 
Queen of Pain.
Keeper of the Light
* Heroes with teleports to escape Solar Blind and Will-O-Wisp: 
Phantom Assassin, 
Puck, Queen of Pain, 
Storm Spirit
Dark Seer
* 
X Marks the Spot prevents Dark Seer or his allies from escaping with Surge.
Keeper of the Light
* 
Crippling Fear prevents Keeper of the Light from using his spells to keep his team alive during team-fights.
* 
Dark Ascension is very strong against Keeper of the Light, as it allows Night Stalker to jump the backline and quickly kill the squishy Ezalor, especially when combined with the slow from 
Void.
Additional:
* Keeper of the Light's 
Aghanim's Scepter upgrade loses much of its power, due to Night Stalker being able to reduce the duration of daytime by a lot.
Keeper of the Light
* Pugna easily copes on the line with the Keeper of the Light push with his 
Nether Blast, and in addition to 
Nether Ward, the Keeper of the Light is not able to throw Illuminate on creeps for a long time, so Pugna earns more gold and a level on the line
Additional:
* Pugna easily copes on the line with the Keeper of the Light push with his Nether Blast, and in addition to Nether Ward, the Keeper of the Light is not able to throw Illuminate on creeps for a long time, so Pugna earns more gold and a level on the line
Keeper of the Light
* Being a cast-oriented hero, Ezalor will suffer from all of Silencer's abilities.
* 
Global Silence is a guaranteed lengthy silence which will render Ezalor useless in a teamfight.
* 
Arcane Curse and 
Last Word are good against any caster, since they are extremely potent.
* However, it should be worth mentioning that a smart Ezalor will buy Eul's Scepter of Divinity to dispel Silencer's abilities. Combined with the level 20 talent (Chakra Magic applies a basic dispel), Ezalor can purge Silencer's abilities off allies and himself alike.
Dark Seer
* The constant dispel from Demonic Purge will make any attempt to save the victim or himself by 
Surge become futile. For what it's worth, Demonic Purge will also dispel 
Ion Shell.
Dark Seer
* A Sniper who is somewhat competent at positioning is hardly going to be affected by any of Dark Seer's spells thanks to 
Take Aim.
* However, an illusion of Sniper made with Wall of Replica is extremely powerful, and hard to deal with.
Dark Seer
* 
Spell Steal will easily steal all abilities from Dark Seer.
Additional:
* Spell Steal can perfect from Rubick's steal all abilities from Dark Seer. Rubick's always purchase Aghanim's Scepter can two stolens abilities from Dark Seer's and waiting for seconds for second stolen abilities (example: combinated Vacuum and Wall of Replica) and many different combination.
* A good positoning from Rubick's Spell Steal waiting steal abilities from Dark Seer 
Wall of Replica and illusion from Wall of Replica Dark Seer's can fighting with effect from outcome steal Wall of Replica from Rubick's.
* Combinated Rubick's steal Surge and 
Blink Dagger is very important catch from Dark Seer's and enemies.
* Rubick's 
Telekinesis can lifted up Dark Seer or enemy heroes and throw to Wall of Replica from Rubick's steal.
Dark Seer
* 
Flame Guard makes Dark Seer not deal any damage with his skills to Ember Spirit.
Keeper of the Light
* Vulnerable spellcasters with no escape mechanisms are easy targets for Huskar: 
Lich, 
Crystal Maiden, 
Silencer, Keeper of the Light, 
Venomancer, etc.
Keeper of the Light
* Heroes with channeling abilities: 
Enigma, 
Witch Doctor, Crystal Maiden.
Keeper of the Light
* With 
Bloodthorn, Clinkz becomes a strong counter to heroes who rely on evasion and blind such as 
Windranger, Phantom Assassin, 
Troll Warlord and Keeper of the Light.
Keeper of the Light
* Jakiro's reliance on his abilities can cause struggles for heroes who rely on evasion or blinds to get upper hand: Phantom Assassin, Windranger, 
Riki, Troll Warlord, Keeper of the Light.
Keeper of the Light
* Heroes with silences: Puck, 
Doom, Riki.
Keeper of the Light
* Any hero who lanes very poorly will struggle with Primal Beast's potential snowball in the very early levels, like Keeper of the Light, 
Luna, 
Templar Assassin...
Dark Seer
* Dark Seer's only disable is Vacuum. Though he starts off with high armor and health, he'll eventually have a hard time dealing with high mobility heroes such as Weaver or Queen of Pain.
Dark Seer
* Abilities that deal low damage with high amounts of instances are irrelevant against Pudge during Flesh Heap's active: 
Gyrocopter's 
Rocket Barrage and Dark Seer's Ion Shell are just a couple examples.
Dark Seer
* Dark Seer relies on Surge for most of his mobility, so he's not very vulnerable to slows, but much more to root effects and walls or pseudo-walls such as 
Disruptor's 
Kinetic Field or 
Slark's 
Pounce.
Keeper of the Light
* Heroes with channeling abilities: Enigma, Witch Doctor, Crystal Maiden.
Dark Seer
* In general, melee heroes without blink mechanisms or spell immunity will have a hard time positioning against Pit of Malice: 
Sven, 
Tiny, 
Wraith King, 
Dragon Knight, 
Meepo, Doom, 
Bounty Hunter, Dark Seer, 
Undying, 
Alchemist, 
Legion Commander.
Keeper of the Light
* Heroes with teleports to escape Solar Blind and Will-O-Wisp: Phantom Assassin, Puck, Queen of Pain, Storm Spirit
Keeper of the Light
* 
Finger of Death can instantly shred many targets, especially fragile Heroes like Keeper of the Light, 
Ancient Apparition or Bounty Hunter.
Keeper of the Light
* Squishy heroes, usually supports, like 
Lion, Ancient Apparition, Keeper of the Light etc can die quickly to Tiny's magic burst.
Keeper of the Light
* Heroes with silences: Puck, Doom, Riki.
Keeper of the Light
* 
Spiked Carapace can be used to reflect Illuminate damage and stun Keeper of the Light.
* 
Vendetta allows Nyx Assassin to follow Keeper of the Light around if he tries to split-push.
* Keeper of the Light is very squishy and will very quickly die to Vendetta and it's followup abilities.
Dark Seer
* Heroes who rely on damage over time as Spiked Carapace can block and reflect only one instance of damage: Venomancer, 
Huskar, 
Ember Spirit, Dark Seer, 
Sand King, Doom, 
Dawnbreaker. However, this also means they are easily stunned.
Keeper of the Light
* 
Rage allows him to be immune to all of Ezalor's abilities. Also, the increased movement speed combined with the slow from 
Ghoul Frenzy and the squishy nature of Ezalor allows Lifestealer to take him down very quickly.
Dark Seer
* Heroes with escape abilities : Anti-Mage Dark Seer Slark Storm Spirit Windranger Weaver can kite Lifestealer due to him having no lockdown
Keeper of the Light
* Juggernaut's 
Healing Ward keeps his team healthy even when pushing against Keeper of the Light's Illuminate.
* Blade Fury can dispel 
Blinding Light, as well as dodge an incoming Illuminate. Juggernaut can attack towers during Blade Fury, so he can dodge an Illuminate without having to stop pushing.
* Should Keeper of the Light obtain 
Will-o-Wisp through purchasing an Aghanim's Scepter, Juggernaut can make quick work of Ignis Fatuus without being interrupted by its pull.
* Keeper of the Light has low health, low armor, and no natural defense against 
Blade Fury.
Additional:
* Blade Fury allows him to be immune to all of Ezalor's abilities.
* Healing Ward heals his entire team, mitigating Ezalor's weak magical burst damage.
Keeper of the Light
* Keeper of the Light's Blinding Light makes Juggernaut miss his attacks. However, it can be dispelled easily with Blade Fury.
Keeper of the Light
* 
Press the Attack can dispel Blinding Light or Solar Bind from a hero.
* 
Duel can be used to instantly take Keeper of the Light out of a team-fight.
Keeper of the Light
* Heroes with abilities that blind or cause Legion Commander to miss will prevent her from winning Duels: 
Arc Warden, Keeper of the Light, Riki, 
Tinker
Dark Seer
* Ion Shell zones out Broodmother in the laning phase, and can kill her spiderlings if used on one Spiderling in a group.
* 
Vacuum can pull Broodmother out of the treeline.
Additional:
* Ion Shell is a very powerful weapon against Broodmother's Spiderlings and makes her laning much harder.
Keeper of the Light
* Illuminate wipes out Broodmother's spiders and prevents her from pushing the lane. It also gives vision to reveal where broodmother is hiding in the trees.
Dark Seer
* Dark Seer's Vacuum and Ion Shell allows him to clear a wave of Terrorblade's illusions.
* Because Terrorblade often builds items that require 
Ultimate Orb like 
Manta Style and 
Eye of Skadi, Dark Seer can create a very strong illusion of Terrorblade with Wall of Replica and 
Normal Punch from Aghanim's Scepter.
* If Dark Seer can use Vacuum to help teammates land their AoE abilities, Terrorblade will be quickly killed before he even gets a chance to use Sunder.
Additional:
* Dark Seer's Vacuum and Ion Shell allows him to clear a wave of Terrorblade's illusions.
* Because Terrorblade often builds items that require Ultimate Orb like Manta Style and Eye of Skadi, Dark Seer can create a very strong illusion of Terrorblade with Wall of Replica and Normal Punch from Aghanim's Scepter.
* If Dark Seer can use Vacuum to help teammates land their AoE abilities, Terrorblade will be quickly killed before he even gets a chance to use Sunder.
Keeper of the Light
* Keeper of the Light can stall pushes with Illuminate. This makes him strong against pushing heroes: Terrorblade Naga siren Nature's Prophet and Anti-Mage
Dark Seer
* Heroes that rely on summons will suffer against Ion Shell, which kills them very quickly: 
Beastmaster, 
Broodmother, Enigma, Nature's Prophet, 
Visage, 
Warlock, Wraith King.
Keeper of the Light
* Illuminate clears Beastmaster's summons and is effective against his push.
Dark Seer
* Heroes who do not have nor rely on passive abilities make Nethertoxin much less effective: 
Clinkz, 
Pugna, Nature's Prophet, Dark Seer, 
Lycan, 
Tusk
Keeper of the Light
* The Keeper of the Light easily farms on the line against the Viper, due to the fact that it has a long-range Illuminate, and the Viper, in turn, cannot use its advantage of dominance on the center line, due to the fact that it does not reach the Keeper of the Light
Additional:
* The Keeper of the Light easily farms on the line against the Viper, due to the fact that it has a long-range Illuminate, and the Viper, in turn, cannot use its advantage of dominance on the center line, due to the fact that it does not reach the Keeper of the Light
Dark Seer
* Dark Seer's Vacuum and Ion Shell can clear a wave of Chen's Creeps effectively.
* Surge applies haste movement and negates the slow from 
Penitence, allowing Dark Seer to easily escape from Chen and his creeps.
* Dark Seer's full combo from Dark Seer's Vacuum, Wall of Replica and Normal Punch from Aghanim's Scepter can often kill Chen or any of his allies before he can save them with 
Hand of God.
Additional:
* Dark Seer's Vacuum and Ion Shell can clear a wave of Chen's Creeps effectively.
* Surge applies haste movement and negates the slow from Penitence, allowing Dark Seer to easily escape from Chen and his creeps.
* Dark Seer's full combo from Dark Seer's Vacuum, Wall of Replica and Normal Punch from Aghanim's Scepter can often kill Chen or any of his allies before he can save them with Hand of God.
Keeper of the Light
* Heroes with summons/illusions/neutral creep armies: Beastmaster, 
Chen, Naga Siren
Dark Seer
* Certain heroes can mess up with Pangolier's positioning and timing (especially if he intends to use Rolling Thunder during combat): 
Vengeful Spirit, Keeper of the Light, Huskar, Dark Seer
Keeper of the Light
* Certain heroes can mess up with Pangolier's positioning and timing (especially if he intends to use Rolling Thunder during combat): Vengeful Spirit, Keeper of the Light, Huskar, Dark Seer
Dark Seer
* Heroes that rely on summons will suffer against Ion Shell, which kills them very quickly: Beastmaster, Broodmother, Enigma, Nature's Prophet, Visage, Warlock, Wraith King.
Keeper of the Light
* Keeper of the Light can stall pushes with Illuminate. This makes him strong against pushing heroes: Terrorblade Naga siren Nature's Prophet and Anti-Mage
Dark Seer
* Heroes that rely on illusions typically spawn very strong illusions inside Dark Seer Wall of Replica that he can use against them or their team: 
Phantom Lancer, 
Chaos Knight, Naga Siren, Terrorblade.
Keeper of the Light
* Keeper of the Light can stall pushes with Illuminate. This makes him strong against pushing heroes: Terrorblade Naga siren Nature's Prophet and Anti-Mage
Dark Seer
* Heroes that rely on summons will suffer against Ion Shell, which kills them very quickly: Beastmaster, Broodmother, Enigma, Nature's Prophet, Visage, Warlock, Wraith King.
Keeper of the Light
* Heroes which rely exclusively on right clicks will struggle somewhat against Blinding Light: Phantom Assassin, Wraith King, 
Medusa
Keeper of the Light
* Heroes with channeling abilities: Enigma, Witch Doctor, Crystal Maiden.
Dark Seer
* Heroes that rely on summons will suffer against Ion Shell, which kills them very quickly: Beastmaster, Broodmother, Enigma, Nature's Prophet, Visage, Warlock, Wraith King.
Keeper of the Light
* Illuminate can wipe the pushing Eidolons in a lane with ease, diminishing Enigma's laning presence by a lot.
* 
Solar Bind will severely slow down Enigma and make him more vulnerable to magical damage more he moves for it's duration.
* However, Keeper of the Light does not have any way to cancel Black Hole outside from Will-O-Wisp from Aghanim's Scepter.
Dark Seer
* Venomancer is a low health hero and low range hero who is easy to harass with Ion Shell on a creep in the early game.
* Venomancer depends entirely on all his slows to keep distance or chase, but since Surge ignores slows, it is nearly impossible for Venomancer to hunt or run away from Dark Seer or his surged teammates.
Dark Seer
* 
Living Armor can be destroyed quickly with Ion Shell.
Dark Seer
* Heroes with haste can negate Enchant's slow: Weaver, Dark Seer, Lycan, 
Centaur Warrunner.
Keeper of the Light
* Heroes with teleports to escape Solar Blind and Will-O-Wisp: Phantom Assassin, Puck, Queen of Pain, Storm Spirit
Dark Seer
* With Normal Punch from Aghanim's Scepter, Dark Seer can gain an advantage against heroes who rely on evasion as Normal Punch has true strike: Phantom Assassin, Windranger, 
Hoodwink.
Keeper of the Light
* Heroes which rely exclusively on right clicks will struggle somewhat against Blinding Light: Phantom Assassin, Wraith King, Medusa
Dark Seer
* Dark Seer can increase the movement speed of allies with Surge, breaking Static Link.
Keeper of the Light
* Heroes with extremely slow movement speed will cripple against Solar Bind: Medusa, 
Viper
Additional:
* Will-O-Wisp will keep Medusa busy after she got hit by Blinding Light.
Keeper of the Light
* 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.
Dark Seer
* With Normal Punch from Aghanim's Scepter, Dark Seer can gain an advantage against heroes who rely on evasion as Normal Punch has true strike: Phantom Assassin, Windranger, Hoodwink.
Dark Seer
* With Normal Punch from Aghanim's Scepter, Dark Seer can gain an advantage against heroes who rely on evasion as Normal Punch has true strike: Phantom Assassin, Windranger, Hoodwink.
Keeper of the Light
* Any hero that can nullify effects of Chronosphere: (Keeper of the Light with Aghanim's Scepter during daytime, 
Winter Wyvern), banishing him or Faceless Void (
Outworld Destroyer, 
Shadow Demon, Earth Spirit with Aghanim's Scepter) or protecting him in other ways (
Dazzle, Oracle, 
Abaddon) can greatly limit Chronosphere's potential.
Keeper of the Light
* Heroes that punish mobile heroes: 
Bloodseeker, Keeper of the Light, Kunkka, Disruptor.
Dark Seer
* Heroes that rely on summons will suffer against Ion Shell, which kills them very quickly: Beastmaster, Broodmother, Enigma, Nature's Prophet, Visage, Warlock, Wraith King.
Additional:
* Surge allows for Dark Seer and his allies to escape from Upheaval due to it ignoring any slow.
Dark Seer
* The haste provided by Dark Seer's Surge or a {Rune:Haste} renders your slows ineffective.
Dark Seer
* Dark Seer can pull together Spectre's illusions with Vacuum, and Wall of Replica creates an illusion of Spectre that deals massive damage.
Dark Seer
* Heroes that rely on illusions typically spawn very strong illusions inside Dark Seer Wall of Replica that he can use against them or their team: Phantom Lancer, Chaos Knight, Naga Siren, Terrorblade.
Dark Seer
* Heroes that rely on summons will suffer against Ion Shell, which kills them very quickly: Beastmaster, Broodmother, Enigma, Nature's Prophet, Visage, Warlock, Wraith King.
Dark Seer
* In general, heroes who are melee with no way to fight back can be very easily poked by Monkey King to gain his Jingu Mastery stacks: Dark Seer, Riki, Rubick.
Keeper of the Light
* Blinding Light can knock Monkey King outside of his ultimate, Wukong's Command and can blind him.
* Will-O-Wisp will stun Monkey King from Tree Dance by destroying his tree.
Additional:
* Blinding Light can easily push Monkey King out of Wukong's Command, as well as blinding him.
* Monkey King is vulnerable to burst damage, Solar Bind makes him more so
* However, Keeper of the Light can be easily ganked by Monkey King during early-mid game stage.
Keeper of the Light
* Heroes that can jump and kill him: Meepo, Clinkz, Templar Assassin
Dark Seer
* Ion Shell destroys 
Refraction's protection stacks in short time.
* Surge ignores the massive slow from 
Psionic Trap.
Keeper of the Light
* Heroes that can jump and kill him: Meepo, Clinkz, Templar Assassin
Dark Seer
* Dark Seer can take great advantage of 
Divided We Stand by putting an Ion Shell on a clone in order to harass them effectively.
* Vacuum can take a single Meepo and disable him for Dark Seer and his teammates to take out.
Dark Seer
* Strong laners are usually at a disadvantage because of how well Sven can jungle. Heroes such as Dark Seer. 
Underlord and Legion Commander may find that later Sven takes care of them very quickly after some jungle farming.
Keeper of the Light
* Melee carries during the laning phase: Sven, Slark
Keeper of the Light
* Heroes with silences: Puck, Doom, Riki.
Keeper of the Light
* Heroes who are strong against mobile heroes: Disruptor, Bloodseeker, Kunkka, Keeper of the Light.
Dark Seer
* Dark Seer relies on Surge for most of his mobility, so he's not very vulnerable to slows, but much more to root effects and walls or pseudo-walls such as Disruptor's Kinetic Field or Slark's Pounce.
Keeper of the Light
* Heroes with dispels: Legion Commander, Oracle, Slark, Phantom Lancer
Dark Seer
* Heroes with AoE abilities will hit Slark in Shadow Dance: Lina, Jakiro, Underlord, 
Leshrac, Dark Seer, 
Earthshaker, 
Timbersaw, Crystal Maiden.
Keeper of the Light
* Melee carries during the laning phase: Sven, Slark
Keeper of the Light
* Heroes with hastes: Dark Seer, Lycan
Keeper of the Light
* Keeper of the Light has a blind, which causes Lycan to miss his attacks.
Keeper of the Light
* Heroes with dispels: Legion Commander, Oracle, Slark, Phantom Lancer
Dark Seer
* Heroes that rely on illusions typically spawn very strong illusions inside Dark Seer Wall of Replica that he can use against them or their team: Phantom Lancer, Chaos Knight, Naga Siren, Terrorblade.
Additional:
* Ion Shell helps taking down illusions quickly, making it easy to identify the real Phantom Lancer.
* Surge allows Dark Seer and his teammates to run away from Phantom Lancer, who relies on his 
Phantom Rush to chase enemies.
Dark Seer
*
Fortune's End dispels Ion Shell and Surge, making any gank attempt on Dark Seer in the laning phase likely to succeed.
Fate's Edict prevents all magical damage that comes from Dark Seer's abilities. 
Fortune's End dispels Ion Shell on creeps, which Dark Seer relies on to farm and zone.
Ion Shell, a skill that helps Dark Seer immensely in the laning phase, as well as 
Surge, a move-speed buff, effectively allowing Oracle to control Dark Seer, especially in the laning phase.
*
*
Additional:
* Fortune's End can dispel
Keeper of the Light
* Heroes with dispels:
Legion Commander, 
Oracle, 
Slark, 
Phantom Lancer