* Heroes that can slow Charge of Darkness by a huge amount: Venomancer, Viper, Dazzle, Arc Warden

* Due to Spirit Breaker's low attack speed, Tombstone is problematic for Spirit Breaker.
* The zombies summoned from Tombstone apply a stacking movement speed slow, which can significantly reduce Greater Bash's damage.
* Soul Rip and Decay allows Undying and his allies to survive from incoming ganks of Spirit Breaker.

* Undying saps strength from heroes with Decay, and Ogre Magi's high strength gain will allow Undying to steal more and more strength, becoming stronger with each use.
* Due to the Strength steal from Decay, Undying is normally very tanky, and has high health, making it harder for Ogre Magi to kill him.

* Arc Warden's Tempest Double is helpful for killing Ogre Magi who lacks AoE damage and disables.

* Generally, any fragile heroes will have a hard time dealing with Undying's tankiness, and even more so if Decay is used on them. Some examples are Crystal Maiden and Witch Doctor.

* Arc Warden's Magnetic Field dodges all damage from Death Ward. Should he choose to buy a Necronomicon, they are quite effective to absorb some shots from your cask, and attack you during Death Ward.

* Magnetic Field makes Impetus miss; if Enchantress decides to enter the field, she is giving up bonus damage since Impetus deals greater damage at higher distance away from targets.

* Spectre must chase for kills and relies on movement speed for mobility in fights, and has no way to counter the Tombstone zombies.
* The potency of Soul Rip can be increased from nearby illusions from Haunt.
* Decay will shut down Spectre during the laning phase by effectively cutting down her initial health pool.
Additional:
* Spectre must chase for kills and relies on movement speed for mobility in fights, and has no way to counter the Tombstone zombies.
* The potency of Soul Rip can be increased from nearby illusions, so Undying can use Haunt against Spectre.
* Early game Decay will make Spectre easy to shut down in lane.

* Undying's Tombstone will cheerfully chew through treants, incidentally netting you some extra income during fights.
* The above interaction tends to ensure that skirmishes are heavily populated with units, thereby buffing Soul Rip

* Sonic Wave is a bad choice in abilities if he and the Tempest Double both use Necronomicon and Blade Mail to reflect the damage to Queen of Pain, potentially killing her outright if her health is low enough.
* Magnetic Field protects himself or his ally from Queen of Pain's attacks unless she has Monkey King Bar.
* One more advantage of Tempest Double is that he can deny himself if he is close to death with Shadow Strike's debuff.

* Decay, Soul Rip and Flesh Golem all deal magical damage which ignores Bulwark.
* Decay reduces Mars' natural strength and therefore his health pool, which is what he relies on to trade effectively in lane.

* Decay's stacking strength reduction makes Axe much less dominant in lane.
* Tombstone's zombies take no damage from Counter Helix, and will continuously put Axe's Blink Dagger on cooldown until dealt with.

* Heroes who can slow and kite Axe will severely inhibit his presence in fights: Bristleback, Crystal Maiden, Batrider, Arc Warden, Winter Wyvern, Clockwerk

* Arc Warden's Flux tears through Refraction charges almost instantly. Should he have a Tempest Double and no creeps are around, a 75% slow means almost certain death.
* Meld is useless against Spark Wraith.
Additional:
* Flux wastes Templar Assassin's Refraction unless she has a Black King Bar or a Manta Style.
* Spark Wraith can be used to bully a Templar Assassin that used Meld.

* Magnetic Field cause attacks from Drow Ranger outside to miss, forcing Drow Ranger to go inside the field, nullifying marksmanship.
Additional:
* Magnetic Field protects Arc Warden and allies from Drow Ranger's ranged attacks. She most likely will not enter the field since she will lose Marksmanship's bonus agility.

* His Tempest Double is not an illusion, but rather a full hero unit, which effectively reduces half of the Supernova's health. His Magnetic Field can tremendously boost his attack speed, allowing him to destroy Supernova in no time even when he's affected by Fire Spirits.
Additional:
* Tempest Double, Magnetic Field's attack speed bonus, and Arc Warden's high attack range will easily destroy a Phoenix using Supernova much faster than usual.
* Phoenix is very weak against pushers, especially those like Arc Warden who can kill him easily, as his skillset works best in teamfights.

* Winter Wyvern cannot handle the Zombies created by Undying's Tombstone very well. In most situations, Zombies will have more movement speed than her.
* Undying can gain one or two easy Decay stacks on an ally in Cold Embrace. The ally will still take the damage as well.
Additional:
* Winter Wyvern cannot handle the Zombies created by Tombstone very well. In most situations, Zombies will have more movement speed than her.
* Undying can gain one or two easy Decay stacks on an ally in Cold Embrace. The ally will still take the damage as well, since it is magical.

* Arc Warden can turn Puck's Phase Shift ability against him by using Spark Wraith, ensuring it to hit. To make this worse, Arc Warden can do it twice with his Tempest Double.
* Flux is also an instant spell (and therefore unavoidable) with a heavy slow and damage over time, which disables Blink Dagger for a certain period of time.

* Anti-Tank heroes like: Razor, Necrophos, Undying.

* Ranged heroes will have a hard time hitting enemies inside Magnetic Field: Silencer, Viper.

* Generally, any fragile heroes will have a hard time dealing with Undying's tankiness, and even more so if Decay is used on them. Some examples are Crystal Maiden and Witch Doctor.

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

* Any hero that can outrange Plague Ward can neutralize them without putting themselves at risk of receiving Poison Sting: Arc Warden, Chen, Clinkz, Drow Ranger, Lina, Mirana, Nature's Prophet, Pugna and Sniper.
* Special mention to heroes has attack range talent can also outrange Plague Ward.

* Arc Warden with his Magnetic Field will protect allies from Mass Serpent Ward.

* Enigma's left level 25 talent (increasing the Eidolon count from three to eleven) powers up Undying's Soul Rip.

* Undying can use Decay not only to reduce Sven's maximum health, but also to reduce the damage he can deal with his ultimate.
* Zombies spawned by Tombstone together with Flesh Golem slow Sven down significantly. Landing Sven's powerful but somewhat slow right-click on Tombstone would be a waste.

* Arc Warden’s Magnetic Field allows him to defend against Terrorblade if he used Metamorphosis.
* Arc also buys a Bloodthorn or a Scythe of Vyse, which can prevent Terrorblade from using his abilities.

* Arc Warden can counter Morphling's strong pushing capabilities by using Magnetic Field to protect buildings.
* Arc Warden also often builds an Orchid Malevolence or Bloodthorn, which can prove dangerous for Morphling.
* Arc Warden can easily break Linken's Sphere with Flux and then slow him with Spark Wraith, making Arc Warden's Tempest Double a legitimate threat as well.

* Magnetic Field prevents Legion Commander from easily gaining wins with Duel.
Additional:
* Magnetic Field prevents Legion Commander from getting wins with Duel.

* Flux will slow and damage Mirana even after she Leaps, since she will likely not be near allies.
* Arc Warden can place Magnetic Field on an ally who has been hit by Sacred Arrow to protect them.
* As Necronomicon is his core item, Arc Warden can reveal Mirana and her allies hiding in Moonlight Shadow and the Necronomicon Warrior can kill Mirana with Last Will if he is unintentionally killed with Starstorm upgraded by Aghanim's Scepter or Sacred Arrow.
Additional:
* If Arc Warden builds Necronomicon 3 he can reveal Mirana's team while Moonlight Shadow is active.
* A Starstorm upgraded by Aghanim's Scepter can accidentally kill a Necronomicon Warrior, which can lead to her death if she hasn't built a Black King Bar.
* Arc Warden can use his summons to prevent Sacred Arrow from hitting himself or his allies.
* Mirana doesn't build items that give armor often, so she usually can't fight against a late game Arc Warden.

* Undying's Decay is a dangerous ability against Bristleback, as it makes him more vulnerable and reduces his tankiness.
* Undying's Tombstone together with Flesh Golem can slow Bristleback down significantly.

* Unlike other illusion heroes, Tempest Double won't be instantly destroyed by Stone Gaze since it is considered a clone and not an illusion.
* He can use either his own or his double's Flux to bypass the spellblock from Linken's Sphere, using the leftover Flux + Spark Wraith to slow Medusa's move speed to a crawl.
* Arc Warden has a farming advantage with double Hand of Midas, and can generally bully Medusa with other items that benefit from duplication.

* Chaos Knight, Lone Druid, Meepo and Arc Warden can be hard targets since Shadow Demon's spells are ill-suited to fight many enemies at once.

* Magnetic Field evades most of Gyrocopter's attacks.
* Necronomicon can kill Gyrocopter with the summons. In addition, Last Will might activate if the Necronomicon Warrior gets killed through Flak Cannon or Call Down.

* Magnetic Field's evasion completely negates Sniper's attacks unless he has True Strike.
* Sniper always positions himself far away from battles, which makes him especially vulnerable for Flux and Spark Wraith.

* Decay can be good against Centaur Warrunner, as reducing the health of Centaur can make Double Edge risky.
* His zombies do not proc Return.

* Heroes with illusions can overwhelm Huskar, as he has no AoE abilities: Phantom Lancer, Anti-Mage, Arc Warden, Chaos Knight.