* Decrepify turns the target ethereal, protecting them from Chaos Knight's and his illusions' attacks.
* Life Drain instantly destroys illusions. It can effectively negate Phantasm when upgraded with Aghanim's Scepter.
* Nether Blast quickly clears out illusions and can harass Chaos Knight in lane.

* Troll Warlord can't switch targets at will, in order to build Fervor stacks, which makes it easy to use Decrepify in order to save allies
* During Battle Trance, Pugna can easily use Nether Blast, Decrepify and Life Drain on him

* Chain Frost can eliminate Chaos Knight's Phantasm army, especially after he clumped up using Reality Rift.
* Frost Shield will heavily reduce his army's effectiveness.
Additional:
* Lich's Chain Frost, especially after obtaining its respective talent that provides unlimited bounces, can take out all of Chaos Knight's illusions quickly.

* Frost Blast and Chain Frost can kite Troll Warlord effectively.
* Frost Shield can single-handedly waste most of the duration of Battle Trance, due to the extreme resistance to physical damage Frost Shield provides. In addition, Troll Warlord is incapable of switching targets during Battle Trance, so he cannot pick an easier target.
* Troll Warlord has little to no ability to regenerate HP, so Frost Blast together with Frost Shield can harass him effectively.

* Berserker's Call and Counter Helix makes short work of Chaos Knight's Phantasms.
Additional:
* Berserker's Call allows Axe to lock down Chaos Knight and his illusions.
* Counter Helix combined with Blade Mail clears illusions out in no time.

* Troll Warlord has significant attack speed due to Fervor and Battle Trance, giving Axe a higher chance to proc Counter Helix and seriously injure Troll Warlord due to his relatively low maximum health.
* Axe often purchases Blade Mail, which can help Axe turn Troll Warlord's farm and high physical damage against him. The bonus armor provided by Berserker's Call means that Troll Warlord will take a lot more damage than Axe.
* Culling Blade is still capable of killing Troll Warlord during Battle Trance if his HP is low enough.
Additional:
* Troll Warlord's high attack speed means Counter Helix will proc extremely frequently even without creeps near him. This, combined with a Blade Mail means Axe can easily solo kill Troll Warlord even in later stages of the game.

* Timber Chain can kite Troll Warlord extremely effectively.
* Whirling Death and Chakram deals lots of damage to Troll Warlord.
* Reactive Armor makes Timbersaw extremely resilient to Troll's attack damage and extreme attack speed, especially during Battle Trance.

* Reactive Armor helps Timbersaw to endure the damage from Chaos Bolt and Reality Rift combo.
* Timbersaw's large amount of pure damage AoE nukes clears Chaos Knight's illusions quickly, drastically reducing his damage.
Additional:
* Strong area damage, particularly from Whirling Death and Chakram, lets Timbersaw clear out illusions quickly.
* Whirling Death directly reduces Strength from both Chaos Knight and his Phantasm illusions, reducing both the damage output and raw health that the hero relies on.
* Reactive Armor quickly builds stacks against Phantasm illusions, making Timbersaw hard to kill.
* Timber Chain allows Timbersaw to escape while surrounded.

* Cold Embrace can protect Troll Warlord's target, especially during Battle Trance.
* Winter's Curse can turn Troll Warlord's high physical damage and attack speed against his allies.
Additional:
* Cold Embrace will protect your ally from being damaged if he gets focused by Troll.
* His high attack speed and bash will help to kill his cursed ally faster.

* Cold Embrace protects targets of Reality Rift.
* Winter's Curse turns Phantasm illusions against Chaos Knight or a teammate.
* Splinter Blast deals decent area damage to Phantasm illusions.
* Arctic Burn's percentage-based damage quickly wears down Chaos Knight's health.
Additional:
* Winter Wyvern can make Chaos Knight's illusions attack the real one, provided the player knows who it is.
* Alternatively, Winter's Curse can make Chaos Knight and all his illusions attack one of his allies.
* Cold Embrace protects ally who is focused by Chaos Knight.
* Splinter Blast deals decent area damage to Chaos Knight's illusions.

* Phantasms can be easily killed with Purification.
* Heavenly Grace dispels the stun from Chaos Bolt and the armor reduction from Reality Rift.
* Guardian Angel works well against Chaos Knight's overwhelming reliance on physical burst damage.
Additional:
* Purification heals a teammate targeted by Reality Rift and heavily damages Chaos Knight and his illusions in the process.
* Guardian Angel blocks all of Chaos Knight's damage for a duration.

* Heroes who rely strongly on melee physical damage will fare badly against Omniknight's Guardian Angel: Sven, Phantom Assassin, Juggernaut, Dragon Knight, Lycan, Ursa, Troll Warlord

* Heroes that rely on physical damage are ineffective against Dragon Knight due to his high armor: Phantom Assassin,Bloodseeker, Lifestealer, Troll Warlord

* Dragon Blood's armor bonus greatly reduces the damage dealt by Phantasm.
* Breathe Fire and Elder Dragon Form's splash damage quickly destroy illusions and reduces their damage output.

* Storm's Dispel Magic combined with Thunder Clap deals high damage against Chaos Knight's illusions even in the late game.
* Chaos Knight's reliance on physical damage is easily hindered by Drunken Brawler.
* Chaos Knight's lack of area effect and mobility makes him easily overwhelmed by Primal Split.
Additional:
* Dispel Magic from {U:Storm} can instantly kill the Phantasm army early game and can still deal a lot of damage to them late game, revealing the real Chaos Knight.

* In general, Brewmaster's Cinder Brew and Thunder Clap makes him good against physical damage carries: Ursa, Clinkz, Faceless Void, Troll Warlord, Templar Assassin, Phantom Assassin.

* Illusion based heroes (like Chaos Knight and Terrorblade) can't use their illusion beneficially against Sanity's Eclipse's high AoE burst damage.

* Outworld Devourer's pure damage from Arcane Orb is very effective at killing Troll Warlord quickly.
* Astral Imprisonment removes Troll Warlord from a fight for four seconds, minimizing his contribution to a teamfight, and potentially wasting over half of Battle Trance's duration.
* Troll Warlord gains a measly 1 intelligence point per level, meaning Sanity's Eclipse is especially effective, often instantly killing him.

* Other heroes that rely on physical attacks to deal damage and not their abilities: Troll Warlord, Sniper, Monkey King, Sven.

* Heroes who rely on illusions can be tagged by Focus Fire: Chaos Knight, Terrorblade.

* Troll Warlord's high speed attack makes Retaliate deal a lot of damage to him.

* Heroes who are reliant on illusions: Chaos Knight, Phantom Lancer, Naga Siren.

* Heroes who are reliant on illusions or summons: Chaos Knight, Broodmother, Naga Siren.

* Heroes who rely heavily on melee attacks and lack early spell immunity are easily blocked and interrupted by Ink Swell: Lycan, Ursa, Troll Warlord.

* Atrophy Aura decreases Troll Warlord's damage.
* Pit of Malice helps lock down Troll Warlord.
* Battle Trance disallows Troll from running out of both Firestorm and Pit of Malice.

* The area of effect damage from Midnight Pulse and Black Hole help deal with Chaos Knight's illusions.
Additional:
* Black Hole usually catches Chaos Knight with all his illusions.
* Midnight Pulse deals damage based on max health, quickly killing Phantasm illusions.

* Ravage damages and disables Chaos Knight's army.
* Anchor Smash deals respectable area damage at early levels and lowers Chaos Knight's damage.
* Kraken Shell dispels Chaos Bolt and Reality Rift while providing protection from damage.

* Fate's Edict can disarm Troll, rendering him useless in a teamfight, especially if he has already used Battle Trance.
* Fortune's End and Purifying Flames can provide ample magic damage to help burst down Troll Warlord quickly in the early to mid game.
* False Promise can save an ally from Troll Warlord's initiation, forcing him to switch targets and lose his Fervor stacks, or waste time during Battle Trance.

* Dark Willow's burst damage and stun prevents Troll Warlord from approaching her until he has Black King Bar.
* Troll Warlord's lack of burst damage makes it hard for him to kill Dark Willow before she slips into Shadow Realm.

* Abaddon could punish Chaos Knight for using Phantasm and Reality Rift combo on him with his Aphotic Shield. Additionally, it provides extra protection against Chaos Knight's potential to take Abaddon down quickly.
* Furthermore, Abaddon's Borrowed Time makes it utterly impossible to burst Abaddon down.

* With his AoE damage, Jakiro can easily kill Chaos Knight's Phantasm illusions.
* Chaos Knight usually doesn't buy a Black King Bar, making him vulnerable to an Ice Path into Macropyre combination.
Additional:
* Ice Path and Macropyre punish Reality Rift with a long stun and heavy damage across all illusions.

* Echo Slam's damage potential increases due to Chaos Knight's Phantasm illusions.
Additional:
* Echo Slam will deal a colossal amount of damage to your army, as will Fissure at lower levels.
* The area stuns from Aftershock will always slow down your illusions, since they can't have spell immunity.

* Maledict cannot be dispelled by Phantasm, and can be used to tag the real Chaos Knight hiding within his illusions.
* If Witch Doctor has an Aghanim's Scepter, Death Ward will bounce between Chaos Knight's illusions, destroying them quickly.
* However, Death Ward is easily interrupted by Chaos Bolt until Witch Doctor buys Glimmer Cape or Black King Bar.

* Chaos Knight's single target abilities are difficult to target against Phantom Lancer's illusions.
* Chaos Knight's lack of mobility makes him an easy target for Phantom Lancer to rush and drain of mana.
Additional:
* Juxtapose allows Phantom Lancer to overwhelm Chaos Knight due to his single-target abilities.
* Doppelganger can be used to dodge Chaos Bolt.
* Spirit Lance can be used to harass Chaos Knight during the early game.
* Since Phantom Lancer build Diffusal Blade often, it can quickly drain Chaos Knight of all his mana, leaving him unable to cast spells.

* Wukong's Command and Boundless Strike combo can easily cause havoc on Chaos Knight by destroying all of his powerful illusions.
* Chaos Knight without Phantasm cannot deal with Jingu Mastery at all.

* Puck's area of effect nukes in the form of Illusory Orb and Waning Rift clears Phantasm illusions from the early game to mid game.
* Phase Shift can be used to disjoint Chaos Bolt.

* Ember Spirit is evasive and can dodge close encounters with melee heroes like Chaos Knight. Ember Spirit can't be caught with the slow from Reality Rift, and Flame Guard and Sleight of Fist can bring Phantasm's illusions down quickly.

* Tidebringer, Torrent and Ghostship destroys Chaos Knight's Phantasm army all through the game.

* Flak Cannon destroys Chaos Knight's illusions very quickly.

* Quill Spray quickly destroys Chaos Knight's Phantasms.

* 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.

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

* Clinkz, Sniper, Lone Druid, Troll Warlord, Legion Commander, Wraith King and others are some of the Heroes that bases themselves on attacks with little or no spell power, suffering in the grassy hands of Overgrowth.

* Heroes that rely on evasion are slightly countered by Desolate: Phantom Assassin, Troll Warlord.

* Heroes that rely on illusions will suffer against Ion Shell, which kills them very quickly: Phantom Lancer, Chaos Knight, Naga Siren, Meepo.
* Heroes that rely on illusions typically spawn very strong illusions inside your Wall of Replica that you should use against them or their team.

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

* Because of his massive AoE damage, Sand King is very effective against illusion heroes: Chaos Knight, Phantom Lancer, Terrorblade,...

Additional:
* Sand King's massive area damage output, particularly Epicenter, allows him to quickly take down Chaos Knight and his illusions.
* He can apply Caustic Finale to illusions with attacks for extra damage.

* Heroes reliant on illusions or summons: Broodmother, Chaos Knight, Naga Siren.

* Heroes who are illusion based, or even heroes who frequently build Manta Style can be cleared quickly by Pangolier's high damage, or lose their damage ouput because of Lucky Shot: Chaos Knight, Naga Siren

* Heroes who cannot fight back during Arena of Blood in the early and mid game: Abaddon, Anti-Mage, Broodmother, Drow Ranger, Luna, Sniper, Troll Warlord, Weaver, Clinkz.

* One of Lion's level 20 talents lets Mana Drain affect 2 secondary targets. This can make things difficult for heroes like Phantom Lancer, Chaos Knight, and Terrorblade who rely on illusion armies.
* Mana Drain and Hex instantly kill any illusions. Finger of Death upgraded with Aghanim's Scepter also shreds most illusions.
* One of Lion's level 20 talents lets Mana Drain affect 2 secondary targets. This can make things difficult for heroes like Phantom Lancer, Chaos Knight, and Terrorblade who rely on illusion armies.

Additional:
* Mana Drain is a real problem to Chaos Knight early game, considering his already low mana pool.
* Aghanim's Scepter upgraded Finger of Death is an AoE ability, which can deal a tremendous amount of damage to his illusions.
* Hex with a level 25 talent instantly disposes Chaos Knight's illusions.

* Heroes who Sniper can kite: Sven, Wraith King, Kunkka, Doom, Tidehunter, Underlord, Troll Warlord, and etc.

Additional:
* Shrapnel and Headshot allows Sniper to kite Troll Warlord effectively.
* Take Aim together with certain items such as Hurricane Pike allow Sniper to sit and fire at Troll Warlord from a safe distance.

* Nightmare and Fiend's Grip help to control/disable Troll Warlord in team-fights.

* Frostbite can disarm and root Troll Warlord if he doesn't have a Black King Bar or a Manta Style to dispel it.
* Crystal Nova and Freezing Field both significantly slow Troll Warlord, making him much more vulnerable to ganks or stuns.
* The magical damage from Freezing Field does a large amount of AoE damage, and Troll Warlord is not capable of cancelling Crystal Maiden's channel.

* Heroes the make heavy use of illusions, like Chaos Knight, Phantom Lancer, or Spectre can suffer from Crystal Maiden, as Freezing Field can quickly kill off the entire horde if not stopped.

* Primal Roar and the slow from Boars makes kiting Troll Warlord very easy.

* With Aghanim's Scepter, Tinker's Laser completely stops Chaos Knight's damage, forcing him to buy either a Black King Bar for his own survivability while leaving his illusions still vulnerable, or a Monkey King Bar leaving him still vulnerable to Tinker's nukes, though improving his damage.
* Tinker rarely finds himself in the middle of a fight, which is where Chaos Knight typically thrives, and even in the rare cases of being so, at level 3 Tinker's constant rearm and blink away can kite and dodge Chaos Knight's spells reliably, so Chaos Knight has very little catch against Tinker's mobility. This gives Tinker impunity to create more chaos in a teamfight than Chaos Knight can control, laying down the field with March of the Machines and constantly being hit by rockets and lasers.
Additional:
* Tinker's Aghanim's Scepter upgraded Laser can blind him and all of his Phantasm illusions.

* Using Reality Rift sets up a Reverse Polarity on Chaos Knight and his illusions.
* Shockwave and Skewer kill Phantasm's illusions quickly, as can Empower cast on a melee carry.
Additional:
* All Magnus abilities are very good against Chaos Knight's Phantasm illusions.