* 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.

* Her illusions with Desolate are very valuable, especially when they are usually paired with Radiance. Unlike blink or force movement, Spectral Dagger's escaping mechanic requires manual movement, and therefore Demonic Purge can hold her back really hard and allow your allies to finish her off.
* If she tries to kill you or any key ally with Haunt at any point of the game, remember to not panic and always use Disruption on the illusion, whether it is fake or the real Spectre herself. When the situation calls, Demonic Purge can save a second victim from a haunting Spectre.
* When upgraded by Aghanim's Scepter, Demonic Purge can remove Spectre from a fight by disabling Desolate and Dispersion, negating her damage and tankiness respectively.

* 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.

* Disruption will save Shadow Demon's teammates from being killed by Counter Helix or Culling Blade.
* Soul Catcher and Shadow Poison can put Axe's Blink Dagger on cooldown.
* Demonic Purge slows Axe to a crawl, making him nearly useless after initiating. If Shadow Demon has Aghanim's Scepter, it will also break Counter Helix.

* 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.

* Heroes that lose a great amount of damage output and become less threatening: Phantom Assassin, Sven, Slark, Phantom Lancer.
* Once you have an Aghanim's Scepter, Shadow Demon instantly reaches a new power spike and becomes a counter for a variety of heroes that have strong passives.
* Heroes that lose a great amount of their tankiness and become easier to finish off: Bristleback, Spectre, Phantom Assassin, Enchantress, Dragon Knight.
* Heroes that lose a great amount of damage output and become less threatening: Phantom Assassin, Sven, Slark, Phantom Lancer.
* You can always stack camps and farm the scepter with Shadow Poison.

* Shadow Demon's Soul Catcher hinders Bristleback's tanking capabilities. Demonic Purge with Aghanim's Scepter disables Bristleback's passives.

* 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.

* 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.

* Heroes with break abilities: Nyx Assassin, Shadow Demon (with Aghanim's Scepter), Viper.

* 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.

* Heroes with ways to protect themselves or allies from Spirit Breaker's initiation: Shadow Demon

* Disruption can banish Faceless Void or an ally in Chronosphere, making it less effective of an ability.
* Faceless Void's illusions created by Disruption will not get stunned by Chronosphere, allowing Shadow Demon to attack Faceless Void in his Chronosphere.
* Casting Disruption after releasing Shadow Poison charges will make Time Walk unable to backtrack the damage.
* Shadow Poison is a good way to deal damage as the initial damage and the release damage can't both be Time Walked at the same time.
* Demonic Purge is a great slow, useful to force out a Time Walk early and can break Time Lock with Aghanim's Scepter.

* 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

* Disruption instantly removes Phantom Embrace, and can potentially save allies affected by Soulbind.
* Demonic Purge dispels Ink Swell.

* Shadow Demon's spammable illusions can be used to scout Techies' Proximity Mines. The illusion of your carries can be even used to trick Techies into detonating his precious Remote Mines.

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

* 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.

* In the laning stage, making illusions of Venomancer will turn his Poison Sting back at him, making for an easy gank at level one, and for later when your mid comes for ganks.

* 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.

* Shadow Demon can waste precious seconds of Windrun with Disruption.
* Alternatively, Demonic Purge can be used to dispel it altogether, leaving her completely defenseless for 7 seconds.
* Disruption can be used to save an ally if they get stunned by Shackleshot.

* 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.

* Similarly, they can negate your X Marks The Spot & Torrent combo by protecting your target when you use Return. Good candidates to negate your combo include Outworld Destroyer and his Astral Imprisonment, and Shadow Demon and his Disruption.
* Heroes with hide abilities can often dodge a Ghostship just before it hits.
* Similarly, they can negate your X Marks The Spot & Torrent combo by protecting your target when you use Return. Good candidates to negate your combo include Outworld Destroyer and his Astral Imprisonment, and Shadow Demon and his Disruption.
* A Eul's Scepter of Divinity can also do the trick, but, unlike the previously mentioned abilities, you can only use it on yourself and not your allies.

* Heroes with a slow attack rate will find themselves struggling to take out Tombstone, like Doom.

* Doom, Disruptor with Aghanim's Scepter, and hex abilities all prevent item usage, which is a severe problem for Phantom Assassin as it prevents her from using Black King Bar, the one item that helps protect her against the aforementioned dangers. Doom and Shadow Demon with Aghanim's Scepter also disables Phantom Assassin's Evasion and Critical Strike, removing much of her damage and survivabaility.

* Heroes with break can disable Untouchable for a while: Doom and Shadow Demon (via Aghanim's Scepter), Viper

* Heroes with high physical damage output but lack of reliable escape mechanisms are always a good target for a solo gank: Sniper, Shadow Fiend, Troll Warlord, Drow Ranger. Those heroes, however, are dangerous if they manage to close the gap, so take caution.

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

* Heroes with high physical damage output but lack of reliable escape mechanisms are always a good target for a solo gank: Sniper, Shadow Fiend, Troll Warlord, Drow Ranger. Those heroes, however, are dangerous if they manage to close the gap, so take caution.

* Heroes that lose a great amount of their tankiness and become easier to finish off: Bristleback, Spectre, Phantom Assassin, Enchantress, Dragon Knight.
* Once you have an Aghanim's Scepter, Shadow Demon instantly reaches a new power spike and becomes a counter for a variety of heroes that have strong passives.
* Heroes that lose a great amount of their tankiness and become easier to finish off: Bristleback, Spectre, Phantom Assassin, Enchantress, Dragon Knight.
* Heroes that lose a great amount of damage output and become less threatening: Phantom Assassin, Sven, Slark, Phantom Lancer.
* You can always stack camps and farm the scepter with Shadow Poison.

* Melee carries such as Sven, Ursa or Lifestealer can be slowed and easily kited with Demonic Purge.

* 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.

* Ursa struggles against heroes with strong (and especially undispellable) disables (Disruptor, Puck, Shadow Demon, Outworld Destroyer and etc).

* Heroes with abilities that can save teammates are also effective such as Shadow Demon, Dazzle, Oracle, Bane, Pugna, Tusk, Winter Wyvern, Io, Underlord, Treant Protector and Keeper of the Light.

Additional:
* Be ready to save an ally from Omnislash with your Disruption.
* Spawning Juggernaut's illusions is a great deal, as his base attack time is low and he has a critical strike. Illusions will benefit from both.
* Demonic Purge will prevent Juggernaut's desperate attempt to flee using Blade Fury. However, it cannot stop him if he is using Town Portal Scroll.

* Heroes that can punish aggressive heroes, such as: Leshrac, Shadow Demon, Pugna, Death Prophet.

* Heroes that can gain vision over trees to catch Tinker: Invoker, Shadow Demon, Batrider

* Heroes with hiding abilities can protect disabled allies: Outworld Destroyer, Shadow Demon, Tusk, Phoenix with Aghanim's Scepter

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

* Disruption can protect Shadow Demon's allies from Fortune's End, preserving healing or buffs. It can also catch Oracle's allies, allowing Shadow Poison and Soul Catcher to be used without being dispelled.
* Demonic Purge prevents over-time healing during False Promise, such as Purifying Flames and Urn of Shadows. If he has Aghanim's Scepter, this issue can persist for longer or on multiple allies.
* It will not, however, prevent healing from instant abilities, items, or auras, making Mekansm a good choice against him.

* Shadow Demon with an Aghanim's Scepter will use Demonic Purge to disable Curse of Avernus and the passive component of Borrowed Time. If this is combined with a silence, Borrowed Time will not trigger at all.
* Even without Aghanim's Scepter, he can still waste Borrowed Time with Disruption. Curse of Avernus fully works on illusions, turning the passive ability against him.

* Heroes that can dominate his illusions or create their own illusions of him: Dark Seer, Morphling, Enchantress, Shadow Demon.

* Shadow Demon, Outworld Destroyer and Tusk can all save a Lasso'd teammate with their defensive spells.

* Heroes who can hide the Dueled target (Outworld Destroyer, Shadow Demon, Tusk, Phoenix with Aghanim's Scepter etc).

Additional:
* Disruption can save allies and mess up an initiation from an enemy Legion Commander. Using Disruption on your ally that is affected by Duel will leave her totally exposed without the benefit of the life steal from Moment of Courage. A precise decision to Disrupt Legion Commander or her victim is crucial to waste Duel's potential.
* Demonic Purge cannot be dispelled by a hard dispel from Press the Attack, which in turn can be dispelled by your ultimate.

* Heroes that can purge buffs can dispel Guardian Angel: Invoker, Shadow Demon, Oracle.

Additional:
* Demonic Purge can dispel Guardian Angel on the key target during combat, allow your allies to finish them.

* Heroes with Break abilities will prevent Slark from regenerating and gaining Essence Shift stacks: Viper, Shadow Demon etc.

* Disruption sets up Anti-Mage for a chain disable. The illusions will deal extra damage due to Mana Break.
* Soul Catcher causes Anti-Mage to take a large chunk of damage, and can hit him when he is inside from Disruption.
* Shadow Poison hits Anti-Mage even after he's Blinked away.
* If Shadow Demon managed to get Aghanim's Scepter, Demonic Purge will disable Anti-Mage's passive skills, making him more vulnerable and it cannot be dispelled.
Additional:
* While it is unwise to encounter Anti-Mage alone, Disruption's considerable cast range can become a perfect setup for any hard-disable to follow up. If he is pinned down, Anti-Mage will quickly face his demise when the illusions deplete his already low mana pool. Manta Style will easily allow him to escape, however.
* The illusions can be controlled to quickly sap mana from any other target, making Anti-Mage one of the most valuable targets to disrupt.

* Disruption can save an ally from a fatal Reaper's Scythe.
* Demonic Purge can remove Ghost Shroud, making Necrophos vulnerable to physical damage and preventing him from regenerating health.

* Heroes with summons or illusions makes Sacred Arrow harder to land: Shadow Demon, Phantom Lancer, Nature's Prophet.

* Heroes with abilities that break Berserker's Blood, lowering Huskar's attack speed and health regeneration: Doom, Shadow Demon, Viper.

* Alchemist is a well-known Radiance carrier among other auras your illusions will benefit from. They also get the extra move speed and reduced base attack time from his Chemical Rage, and it's even better if you can catch him as his own rage is about to expire.
* Disruption will buy enough time for all allies to retreat when Alchemist starts to activate Unstable Concoction.

* Heroes with summons or illusions to counter Flux, such as {Hero ID:Beastmaster} , Chen, or Shadow Demon.