* Dark Seer's Vacuum and Ion Shell can clear a wave of Chen's Creeps effectively.

* Illusion and heroes with summons are difficult to kill with Chen's single-target offensive spells: Terrorblade, Phantom Lancer, Chaos Knight, Broodmother, Naga Siren, Lycan, Visage. However, Chen can convert enemy summons with Holy Persuasion, as long as they don't bunch up.

* Viper has no response to the standard initiation combo of Reality Rift into Chaos Bolt.
* Phantasm and Chaos Strike can eliminate Viper almost instantly with it's damage output.
Additional:
* As Viper focuses on single-target damage, he has trouble fighting off Phantasm illusions.
* Reality Rift counteracts Viper's slows and reduces his durability.

* Heroes who do not have nor rely on passive abilities make Nethertoxin much less effective: Clinkz, Pugna, Nature's Prophet, Dark Seer, Lycan, Tusk

* Dark Seer can increase the movement speed of allies with Surge, breaking Static Link.

* Razor has no way to deal with Chaos Knight's multiple illusions from Phantasm.

* Multiple attackers thanks to illusions: Phantom Lancer, Chaos Knight, Naga Siren (bonus for her Ensnare). Also despite the visual effects, Templar Assassin does not spill damage against illusions or buildings, so she is not a really good hero to clean up illusions.
* Heroes that can quickly deal damage to her, regardless of how weak they are, can easily break through her Refraction:
* Multiple attackers thanks to summoned units or clones: Meepo, Witch Doctor, Lycan, Enigma, Shadow Shaman
* Multiple attackers thanks to illusions: Phantom Lancer, Chaos Knight, Naga Siren (bonus for her Ensnare). Also despite the visual effects, Templar Assassin does not spill damage against illusions or buildings, so she is not a really good hero to clean up illusions.
* Weak damage but high tick rate or persist in a long time: Slark, Gyrocopter, Queen of Pain, Shadow Shaman (Shackles), Jakiro, Pugna

* Ion Shell destroys Refraction's protection stacks in short time.
* Surge ignores the massive slow from Psionic Trap.

* Surge allows for Dark Seer and his allies to escape from Upheaval due to it ignoring any slow.

* Warlock is a very strong hero when positioned correctly, and his long cast range helps him with this. However, some Heroes might disrupt or sneakily pass through your allies and deal with you, preventing you from doing your job. Such heroes include Chaos Knight, Spirit Breaker, Riki, and some others.

* 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 them for him and his teammates to take out.

* Dark Seer's Vacuum and Ion Shell allows him to clear the wave of Terrorblade's illusions.
* Wall of Replica can create stronger illusions of Terrorblade.
* If Dark Seer can use Vacuum to help teammates land their AoE skills, 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.
* Wall of Replica can create stronger illusions of Terrorblade.
* If Dark Seer can use Vacuum to help teammates land their AoE skills, Terrorblade will be quickly killed before he even gets a chance to use Sunder.

* 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.

* Phantasm's illusions can be used to push towers and force Techies to detonate Remote Mines.
* Phantasm's illusions can be used to sweep Proximity Mines and Stasis Traps.
* Chaos Knight can easily kill a lone Techies before they Blast Off!.

* While Chaos Knight can land far away from Rubick due to Telekinesis, it can be counteracted by Reality Rift.
* Phantasm dispels Fade Bolt's damage reduction debuff.
* Rubick is fragile and can easily be killed by Chaos Knight and Phantasm's illusions, before he retaliates.

* Morphling is mostly a single target damage dealer with low mobility and no wave clear, this leave him vulnerable to Chaos Knight illusion from Phantasm.
* A long duration stun from Chaos Bolt coupled with Reality Rift and high damage output from Phantasm can easily burst down Morphling before he can shifts Agility to Strength.
* Chaos Knight often buys Bloodthorn, rendering Morphling useless for 5 seconds (unless he has Linken's Sphere or Manta Style )

* Heroes with AoE abilities will hit Slark in Shadow Dance: Lina, Jakiro, Underlord, Leshrac, Dark Seer, Earthshaker, Timbersaw, Crystal Maiden

* Dark Pact is minimally effective against Phantasm illusions, and Slark lacks area damage otherwise.
* Pounce can be counteracted by Reality Rift.
* Slark is naturally frail and dies quickly to Chaos Knight's burst damage before he can build Essence Shift stacks.
* Be aware, however, that Shadow Dance can make Slark hard to kill as he can't be targeted during its duration.
Additional:
* Phantasms have enough health to survive Dark Pact, and Slark has no other source of AoE damage to deal with them.

* Phantasm's illusions make it difficult to land Meat Hook and Dismember.
* Chaos Bolt is a comparatively low cooldown tool to interrupt Dismember.
* Chaos Strike's lifesteal offsets Rot's damage.

* Casting Phantasm before a fight minimizes the disruption from Global Silence.
* Because Chaos Knight generally relies on attack damage, Silencer's spells won't be as effective against him.

* Reality Rift will disable Drow Ranger's Marksmanship, along with Chaos Bolt he can keep her locked for enough time to be killed.
* Phantasm's illusions are hard for Drow Ranger to deal with as she lacks of AoE damage.

* Life Drain does not instantly kill the illusions from Phantasm
* Chaos Bolt easily interrupts the channeling from Life Drain
* Reality Rift makes it harder for Pugna to keep his distance
* Nether Ward barely deals any significant damage on Chaos Knight
* The overwhelming damage of Chaos Knight and his illusions will do a quick work on Pugna's poor HP poll, or safely remove the Nether Ward from the battlefield

* Phantasm dispels Track, and the illusions make it difficult to Track the real Chaos Knight.
* Bounty Hunter is fragile and can easily be killed by Chaos Knight and Phantasm's illusions.

* 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 Surge ignores slows, so is nearly impossible to hunt or run away from Dark Seer or his surged teammates.

* Chaos Knight can dispel Flux with Phantasm.
* Chaos Knight can use Reality Rift to pull Arc Warden out of Magnetic Field.
* Once Chaos Knight jumps on Arc Warden with Reality Rift, Arc Warden struggles to escape due to low mobility.

* Phantasm dispels Ignite and makes targeting the real Chaos Knight much harder.

* Chaos Knight's Level 20 Talent: Reality Rift Pierces Spell Immunity allows for quick bursting down of Lifestealer during his Rage.
* Phantasm dispels Open Wounds.
* Lifestealer has no way of dealing with Chaos Knight's illusions.
Additional:
* Level 20 talent allows Reality Rift to bypass spell immunity provided by Rage, thus negating the advantage Lifestealer has in his kit.
* Lifestealer lacks wave clearing and reliable lockdown makes it difficult to fight Chaos Knight's illusion.
* Feast is largely negated by Chaos Knight's high burst damage in Chaos Strike.

* While Blade Fury is on cooldown, Juggernaut can be easily killed by a standard Chaos Bolt & Reality Rift combo.
* Phantasm illusions can tank Omnislash.

* Chaos Knight's high health pool makes him resistant to Zeus' burst damage. Phantasm can dispel Veil of Discord, a typical item purchased by Zeus.
* Zeus is easily overwhelmed by Chaos Knight's strong illusions, as Arc Lightning is not enough to kill them fast enough to have any impact.
* Zeus' low base armor makes him extremely vulnerable to Chaos Knight's high damage output and armor reduction.

* Reality Rift pulls out Night Stalker while he tries to escape or chase.
* Night Stalker doesn't have a lot of ways to deal with multiple targets, which makes him vulnerable to Phantasm illusions from early to mid game, until Night Stalker buys Aghanim's Scepter.

* Ursa has no way to clear illusion quickly, making him vulnerable to Chaos bolt and Phantasm combo.
* Reality Rift can quickly relocate or reinitiate on Ursa once the duration of Enrage is over.
* Phantasm can be used to dispel Earthshock's slow. Manta Style is another item that counter Ursa greatly.
* Ursa has low mobility, once jumped on by Reality Rift, Ursa struggles to escape.
Additional:
* Ursa cannot effectively fight against Phantasm's illusions with his single-target damage.
* Chaos Bolt's potentially long stun with Chaos Bolt gives Ursa little opportunity to Enrage.

* Wraith King has no form of AoE to clear Chaos Knight's illusions from Phantasm.
* Wraith King is very vulnerable if he reincarnates in the middle of his illusions.

* Living Armor can be destroyed quickly with Ion Shell.

* Dark Seer can pull together Spectre's illusions with Vacuum, and Wall of Replica creates an illusion of Spectre that deals massive damage.

* Single-target disablers will have difficulty locking down a Chaos Knight with Phantasm active: Bane, Beastmaster, Bloodseeker, Clockwerk, Doom, Shadow Shaman.

* Single-target disablers will have difficulty locking down a Chaos Knight with Phantasm active: Bane, Beastmaster, Bloodseeker, Clockwerk, Doom, Shadow Shaman.

* Heroes who relies on illusions and summons (Beastmaster, Chaos Knight, etc.).

* Skywrath mage also has a terrible time fighting against anything that isn't a hero. As Mystic Flare only affects heroes, 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.

* Phantasm gives Chaos Knight a significant advantage against single-target damage dealers: Lifestealer, Wraith King, Night Stalker, Troll Warlord.

Additional:
* Chaos Knight's tanky illusions easily take advantage of Troll Warlord's lack of AoE damage.
* Chaos Bolt can stun Troll for up to 4 seconds and Reality Rift prevents Troll Warlord from chasing down foes.
* Phantasm increases Chaos Knight's physical damage output up to 4 times and can easily kill Troll Warlord before he has a chance to use Battle Trance or a Black King Bar.

* Chaos Knight's multiple illusions from Phantasm can destroy Undying, as Soul Rip can't offset the damage from the high amount of damage from his illusions.

* Heroes that can overwhelm Visage by sheer number like Chaos Knight, Meepo, Terrorblade and Phantom Lancer.

* Single-target disablers will have difficulty locking down a Chaos Knight with Phantasm active: Bane, Beastmaster, Bloodseeker, Clockwerk, Doom, Shadow Shaman.

* Heroes with illusions and summons can be hard for Phantom Assassin to deal with, as she lacks any AoE abilities to deal with them without items: Broodmother, Phantom Lancer, Chaos Knight, Naga Siren, Terrorblade.

* Heroes with illusions and summons can swarm Bane, who has no area abilities: Broodmother, Chaos Knight, Nature's Prophet, Phantom Lancer, Terrorblade.

Additional:
* Phantasm's illusions make it difficult for Bane to target Chaos Knight with Nightmare, Brain Sap and Fiend's Grip.
* Chaos Bolt is a comparatively low cooldown tool to interrupt Fiend's Grip.
* Nightmare can be transferred by Phantasm illusions.

* Heroes with illusions can overwhelm Huskar: Phantom Lancer, Anti-Mage, Arc Warden, Chaos Knight.

Additional:
* Huskar's low armor and movement speed make an easy target for Chaos Knight to initiate on with Reality Rift and Chaos Bolt.
* Beside Inner Fire, Huskar has no reliable AoE ability to clear Phantasm illusions.
* Huskar likes to fight at low health to benefit from his Berserker's Blood, thus vulnerable to Chaos Knight's high burst physical damage.

* Single-target disablers will have difficulty locking down a Chaos Knight with Phantasm active: Bane, Beastmaster, Bloodseeker, Clockwerk, Doom, Shadow Shaman.

* Ion Shell is a very powerful weapon against Broodmother's Spiderlings and makes her laning much harder.
Additional:
* 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.

* Phantasm removes Glimpse and dispels Thunder Strike. Additionally, the Phantasm illusions make it difficult to use Glimpse and Thunder Strike on the real Chaos Knight.
* Disruptor's lack of mobility, combined with his lack of innate defense, sets him up for a Reality Rift and a beatdown by Chaos Knight and his illusions.

* While Legion Commander has a decent nuke in her Overwhelming Odds, Chaos Knight's tanky illusion can easily withstand the damage and retaliate.
* Chaos Knight's long duration stun and massive single target damage output can easily kill Legion Commander before she can counter-initiate with Duel.

* Innately fragile heroes will die almost instantly to Reality Rift while Chaos Knight has illusions active: Drow Ranger, Bane, Necrophos, Crystal Maiden.

* 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

* Heroes with illusion and clone abilities may confuse Bloodseeker, causing him to waste time in fights: Phantom Lancer, Chaos Knight, Arc Warden

* Sniper is very fragile, along with his low movement speed, make an exceptionally easy target for Chaos Knight to initiate on.
* Sniper has no innate ability to deal with Phantasm or escape a Reality Rift and Chaos Bolt combo.
* In most cases, Sniper likes to stay far in the backline to deal damage, thus he is vulnerable if Chaos Knight manage to jump in the back line. This usually spells a quick end for Sniper.

* 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.

* 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.

* 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.