* Heroes with channeling abilities: Enigma, Witch Doctor, Crystal Maiden.

* 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.
* However, Mana Burn's Mana Burn can be more or less mitigated with Chakra Magic.

* 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.

* Heroes with damage burst can often kill Chen or his allies before he can use Hand of God: Lina, Luna, Techies, Shadow Fiend, Pugna, Nyx Assassin.

* As a counter to most casters,Nyx will shut down Muerta with only a few items.
* Nyx's Mana Burn can make short work of Muerta's high intelligence pool.
* Spiked Carapace and Vendetta can help Nyx escape or imitate when needed.

* Level 4 Mana Burn burns of Medusa's mana every 5 seconds if Medusa only increases her mana pool with intelligence. Additionally, 70% of the Mana Burn damage gets mitigated by Mana Shield, burning even more mana.
* Due to the passive nature of Mystic Snake and Split Shot, it can possibly proc Nyx's Spiked Carapace if he's within range of Medusa's abilities and isn't invisible.
* Medusa lacks single target damage, making Nyx with Aghanim's Scepter extremely hard to deal with if Medusa is the team's main damage source.
Additional:
* With her passive Split Shot, Medusa can be easily interrupted by Spiked Carapace during combat, especially during her precious Stone Gaze.
* Mana Burn quickly destroys Mana Shield, especially if Medusa only increases her mana pool by bolstering intelligence (which has the added bonus of increasing Mana Burn's damage).
* Uncontrollable damage from Mystic Snake and Split Shot can trigger Spiked Carapace.
* Medusa lacks single target damage, making a Burrowed Nyx Assassin hard to kill.

* Vendetta can deal great damage against her. However, it requires an direct attack, so Nyx Assassin may have difficulties applying Vendetta on her.
* Enchantress's lack of mobility makes her a primary target for ganking with Vendetta.
* Spiked Carapace can reflect Impetus and stun Enchantress.
* Mana Burn can deal tremendous damage against her due to being an Intelligence hero.
Additional:
* Spiked Carapace reflects the damage from Impetus.
* Enchantress is a rather squishy hero, making her fall easily to Nyx Assassin's high burst damage.

* A good Nyx can reflect Queen of Pain's Sonic Wave with his Spiked Carapace, or even initiate a gank on her in Vendetta while she farms a creep wave with Scream of Pain.
* Her strength to intelligence ratio is bad enough that he should be able to kill her without even requiring a Dagon, provided he can get his full combo off.

* Death Ward with Aghanim's Scepter makes quick work of the spawned illusions from Disruption.
* However, it can be cancelled by Disruption until Witch Doctor buys Linken's Sphere or Black King Bar.
* All of Witch Doctor's abilities are active, making Demonic Purge break from Aghanim's Scepter useless.
* Voodoo Restoration can out-heal the damage from Shadow Demon's abilities.
* An attempt to save an ally using Disruption can easily become a perfect setup for a Maledict or Paralyzing Cask for the enemy.

* Nether Blast's animation makes it easy to time Spiked Carapace for a stun.
* Pugna has the largest intelligence gain in the game, making him a prime target for Mana Burn.
* Pugna needs to channel Life Drain, making him easy to hit with Impale.
Additional:
* Due to Pugna's incredible intelligence growth and terrible strength growth, Nyx should always be able to take you out with his combo, with or without an added Dagon. Mana Burn will deal a large amount of damage in particular, especially in the late game.
* Spiked Carapace is also a great tool versus Pugna. A good player will wait for you in Vendetta until you farm a creep wave with Nether Blast and reflect it back at you as their initiation and setup for Impale.

* 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.

* Nyx's Spiked Carapace can reflect the damage of Sharpshooter, instantly killing hoodwink. Nyx can also use Vendetta to position himself in such a way to screen allies from Sharpshooter and catch Hoodwink by surprise.

* Nyx can walk into Firefly with Spiked Carapace and stun Batrider if he has no Spell Immunity, even if Batrider is focusing on other enemy hero.

* Nyx Assassin takes advantage of Invoker's massive intelligence gain and mana pool to do tons of damage using Mana Burn, as the spell does more damage based on the target's intelligence.
* Nyx Assassin can simply activate Spiked Carapace while under many Invoker's abilities to stun him.

* Spiked Carapace stops Snapfire's Mortimer Kisses.

* Mana Burn removes much-needed mana for Ball Lightning.
* Spiked Carapace triggers on Static Remnant for an easy stun.
Additional:
* Mana Burn is capable of removing most of Storm Spirit's large mana pool, along with dealing heavy damage and quickly depleting his chances of escaping a gank or fight.

* Crystal Maiden has a very bad movement speed, so Impale is easy to land against her. Furthermore, even while trapped by Frostbite, Nyx Assassin can still cast Impale.
* Crystal Maiden has very low armor, so Vendetta is very effective.
* Nyx Assassin has two ways to stop Freezing Field, provided she doesn't get a Black King Bar. He can either pop Spiked Carapace and simply walk into the field, or he can use Impale to interrupt the field, since Crystal Maiden has to channel it.
Additional:
* Spiked Carapace easily interrupts Freezing Field.
* Frostbite's damage over time sets up an easy Spiked Carapace stun.
* Crystal Maiden is extremely fragile and dies quickly to Nyx Assassin's burst damage.

* Nyx Assassin's Spiked Carapace will stun Leshrac when hit by any of his AOE abilities.
* Mana Burn deals high damage due to Leshrac's high intelligence gain and burns a large amount of Leshrac's essential mana pool.

* Spiked Carapace allows Nyx to get an easy long-duration stun on Weaver once he uses Shukuchi, and then he can follow up with Impale.
* Vendetta works as a great setup for both Impale and Spiked Carapace and can deal decent damage to Weaver. Additionally he can neutralize The Swarm beetles due to his invisibility duration.

* Outworld Destroyer's high intelligence gain and fragility makes him an easy target for a massive Mana Burn, as well as killing him outwards with Nyx Assassin's high burst damage.
* Astral Imprisonment can be easily exploited by Nyx Assassin with his abilities. As long as Astral Imprisonment was not cast on Nyx Assassin, it will make an opportunity for an easy stun, either by Spiked Carapace (if Outworld Destroyer hid his allies or your allies) or Impale (if he hid himself). If Astral Imprisonment was cast on Nyx Assassin, using Spiked Carapace while banished will proc the stun after the disable, since Spike Carapace has a 0 second cast time and Astral Imprisonment deals damage right after the disable ends.
* An ill-timed Sanity's Eclipse and/or well timed Spiked Carapace can deal a lot of damage to Outworld Destroyer and stun him, unless Outworld Destroyer used Black King Bar beforehand.
Additional:
* Outworld Destroyer's high mana pool and high intelligence makes him a prime target for Mana Burn.
* If timed correctly, Spiked Carapace will return the full damage from Sanity's Eclipse back to Outworld Destroyer. Even a reflected Arcane Orb can deal significant damage and make him vulnerable to a follow-up from Nyx Assassin.
* Spiked Carapace is also the perfect tool against Astral Imprisonment: if used on Nyx, he can reflect the damage back as he comes out of the prison by casting the ability while imprisoned.

* Nyx Assassin has a lot of burst damage from his Impale, Mana Burn, Dagon, and the bonus damage from Vendetta. All of this damage is enough to kill Drow Ranger.
* Nyx Assassin is usually invisible most of the time thanks to his ability Vendetta, which allows him to gank Drow Ranger easily.

* Nyx Assassin's high burst damage can be the bane of Dark Willow, as her low health makes it difficult to survive long enough to escape through Shadow Realm.
* Spiked Carapace can be triggered by walking deliberately into Bramble Maze, leaving Dark Willow stunned and defenseless.

* 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.

* Heat-Seeking Missile allow easy Spiked Carapace stuns.
* As a fragile hero that relies on mana and intelligence items, Tinker is vulnerable to Mana Burn.
* Nyx Assassin's stuns can interrupt Rearm and leave Tinker helpless.
Additional:
* Nyx Assassin's whole skillset is good against Tinker:
* Impale prevents Tinker from blinding Nyx Assassin or fighting back, while giving Nyx' allies time to catch up to Tinker's position.
* Mana Burn generally deals more damage to intelligence based heroes like Tinker.
* Spiked Carapace can stun Tinker at a moment of Nyx Assassin's choosing if March of the Machines has been cast. It is also quite easy to time Spiked Carapace against Heat Seeking Missiles.
* Vendetta allows Nyx to approach Tinker in the trees or wait for him in common hiding spots and deal heavy damage to his low armor.

* Heroes who have channeling abilities because Terrorblade has no disables to cancel them at all and does not like buying disabling items at all: 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.

* Nyx Assassin deals large amounts of pure damage with Vendetta and magical damage with Impale and Mana Burn, allowing him to ignore Terrorblade's armor and burst his low health pool down before he can use Sunder.
* Nyx Assassin commonly buys Urn of Shadows, Dagon and Meteor Hammer which deal magic damage that ignore Terrorblade's armor.
* Mana Burn might drain too much mana for Terrorblade to be able to use Sunder if he isn't careful in the early to mid game.

* Large area-of-effect with delay or require channeling: Enigma, Crystal Maiden, Invoker, Shadow Fiend, Pugna, Keeper of the Light, Dawnbreaker.

* Heroes that can pick you off: Clinkz, Nyx Assassin, Puck, Riki.

* Nyx Assassin, Bounty Hunter and Slark can all sneak up and kill Shadow Shaman, Nyx being particularly deadly. Shadow Shaman must watch out for Slark carefully, as he can break either (but not both unless he makes a mistake) of Shadow Shaman's disables, with Dark Pact and leap out of a serpent ward ring. These heroes, however, rely heavily on escape and are themselves not very durable and none of them can survive a full lockdown with Mass Serpent Ward. Having Sentry Wards can turn Shadow Shaman from prey to predator.

* 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.

Additional:
* Enigma's uncontrollable damage from Malefice and Midnight Pulse make him easy to stun with Spiked Carapace.
* Black Hole can be easily interrupted by Impale or Spiked Carapace.

* Slow-moving projectiles: Skywrath Mage, Tinker, Necrophos

Additional:
* Skywrath Mage's low health makes him rather easy prey for Nyx Assassin and his lack of armor generally means he'll take the full brunt of a Vendetta strike.
* Mana Burn is annoying at all stages of the game as it turns Skywrath Mage's high intelligence growth against him.
* Spiked Carapace gives Nyx some degree of protection against Skywrath's spells.

* Heroes with either magical, physical or pure damage burst: Bane, Ember Spirit, Leshrac, Lina, Luna, Nyx Assassin, Phantom Assassin, Skywrath Mage, Tinker, Ursa, Void Spirit.

* Assassinate is easy to reflect with Spiked Carapace for massive damage.
* Shrapnel's area damage can set up an easy stun with Spiked Carapace, especially when combined with Vendetta.
* In the early game, Sniper's low health pool and high intelligence makes him easy prey for Nyx Assassin.

* Vendetta allows Nyx to sneak up on Lion and deal massive damage to him, especially when followed up with an Impale, Mana Burn, or even Dagon.
* Spiked Carapace has the potential to not only nullify Lion's damage, but also cripple and potentially deal massive damage to Lion, especially if he reflects Finger of Death.

* With Vendetta, Nyx Assassin can move closely to Ember Spirit when he's farming with his Flame Guard and use Spiked Carapace with Impale to provide a reliable and long disable.
* Mana Burn is also good, as Ember Spirit relies on his limited mana pool for the early to midgame.
Additional:
* Spiked Carapace can be easily triggered by Flame Guard or Battle Fury, setting up a deadly Impale.

* Illusory Orb is easy to reflect with Spiked Carapace, either stunning Puck and setting up an easy Impale or forcing a premature Phase Shift.
* Puck is an intelligence hero that tends to build intelligence items, making it vulnerable to Mana Burn.
* An ill-timed Phase Shift can easily set Puck up to be stunned by Impale.
* Puck's low base armor and below average agility gain mean it is always susceptible to Vendetta.
Additional:
* Nyx Assassin can take advantage of every one of Puck's weaknesses. His entire skill set is very effective in countering Puck.
* Because Illusory Orb is such a slow moving projectile, Nyx Assassin can simply walk into the orb and activate Spiked Carapace, stunning Puck and setting up an easy Impale. This can be circumvented by using Phase Shift while the orb is traveling, however, that means that Puck cannot use Phase Shift to dodge any other skill nor use it to safely blink away from a fight.
* Puck is an intelligence hero that likes to build intelligence items such as Eul's Scepter of Divinity, Scythe of Vyse, and Dagon. This makes Mana Burn that much more deadly against Puck.
* An ill-timed Phase Shift can turn into an easy setup for Impale.

* Many of Nyx Assassin's abilities are good against Windranger.
* Impale is great for stunning Windranger and allowing additional disables to be landed.
* Mana Burn is useful against Windranger's decent intelligence growth and also burns some mana, preventing her from using more abilities.
* Spiked Carapace is easy to use against Powershot.
* Vendetta allows Nyx Assassin to sneak up on and deal massive damage to Windranger without giving Windranger a chance to use Windrun to evade it.
* Nyx Assassin's item build allows him to easily deal with Windranger.

* Voodoo Restoration heals to counter Bloodseeker's Thirst.
* Rupture is generally useless against Witch Doctor while he is staying on Death Ward.
* Although Witch Doctor needs to be careful as Blood Rite can interrupt Death Ward.

* Mana Burn drains Pudge's little mana which may render Meat Hook and Dismember unusable.
* Impale and Spiked Carapace can be used to cancel Dismember easily, and can even do so when Pudge uses it on Nyx Assassin, if timed correctly.

* Mana Burn does tons of damage against Lina because of her high intelligence. The mana burn also prevents Lina from casting her full combo.
* Spiked Carapace can easily be used to counter Lina's abilities because of their long cast animation, and could probably kill Lina outright if Laguna Blade is reflected.

* The huge physical damage taken from Vendetta will force Necrophos to use Ghost Shroud, which is good for a followup with Dagon and Ethereal Blade, both of which are common items on Nyx Assassin.
* Using Ghost Shroud also sets Necrophos up for a Mana Burn or Impale.

* Spiked Carapace reacts on any of the damage over time from Phoenix's abilities and can interrupt Sun Ray and Icarus Dive.

* Spiked Carapace can stop Dawnbreaker's Solar Guardian which will eliminate her global presence and limits her movement around the map.
Additional:
* Spiked Carapace interrupts Starbreaker before Dawnbreaker has her Aghanim's Shard, as well as Solar Guardian during the initial channel, making her ineffective at joining and dealing damage in teamfights.
* The slow projectile and damage over time effect of Celestial Hammer makes it easy to stun Dawnbreaker if she attemps to engage or chase.

* Voodoo Restoration heals to counter damage over time of Poison Nova and Poison Sting.

* Impale and Spiked Carapace interrupts Upheaval with ease.
* Warlock's low health pool, mobility, and high intelligence gain makes him a prime target for Nyx Assassin's burst damage.

* Heroes with heavy early and mid-game magical damage are also problematic for Phantom Assassin due to being able to easily kill her before she gains an item advantage: Lina, Necrophos, Nyx Assassin, Gyrocopter. Should be noted these heroes are usually quite squishy and don't scale well with health. So to some respect, they are on a time crunch.

* Heroes with invisibility: (Riki, Clinkz, Nyx Assassin.

* Another hero that should not leave a special circle for his ultimate. The only thing to be afraid is Boundless Strike.

* Multiple attackers thanks to summoned units or clones: Meepo, Witch Doctor, Lycan, Enigma, Shadow Shaman
* 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

* Mana Burn can instantly deplete Tidehunter's low mana pool, especially in the early game, potentially preventing Tidehunter from casting Ravage.
* Ravage's travel time allows Nyx Assassin to easily stun Tidehunter with Spiked Carapace.

* Voodoo Restoration heals to counter damage over time of Viper abilities.
* Viper has no way to cancel Death Ward, even through Rod of Atos.

* Vendetta disables Vengeance Aura and allows him to attack Vengeful Spirit with Impale and Mana Burn.
* Spiked Carapace is easy to use against a Wave of Terror or Magic Missile.

* 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.

* 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.

* Paralyzing Cask can save ally from Legion Commander Duel's until she purchase Aghanim's Scepter.
* Voodoo Restoration can heal Witch Doctor allies from Duel's.
* Death Ward can help Witch Doctor allies from winning Duel's, if, he is not a target.

* Last Word is extremely easy to reflect with Spiked Carapace for large amounts damage, due to triggering when Nyx Assassin casts a spell, but can still silence Nyx Assassin. It also has the added bonus of dealing more damage the more Intelligence Silencer has.
* Glaives of Wisdom quickly builds Silencer's Intelligence, making him a particularly prime target for Mana Burn.
* Silencer rarely builds survivability items, nor is he able to steal much Intelligence while surrounded by his team, and so is an excellent target for Vendetta.
* Silencer has no reliable way of dealing with a burrowed Nyx, and also lacks the ability to prevent Nyx from escaping with Vendetta,
Additional:
* Silencer is rather squishy and has poor mobility without items, making him an easy target for Nyx.
* Silencer's intelligence steal ability is a complete disadvantage against Nyx Assassin as Mana Burn will deal increasing damage for each point of intelligence Silencer has stolen, turning Silencer's intelligence steal against him.

* Nyx Assassin can reflect Life Break with Spiked Carapace.

* 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.

* Paralyzing cask bounces between him and his wolves, keeping him stunned for long amounts of time.