* Timbersaw's innate tankiness is very hard to deal with as Naga Siren. Timbersaw's high Pure Damage and spammable AoE nukes can also destroy Naga Siren's illusions very fast.

* Reactive Armor helps Timbersaw sustain harassment from Stifling Dagger, as well as ganking attempts.
* Phantom Assassin is a hero with moderate HP pool, and usually appears in the front line of battle. Because Blur does nothing against spells, she is vulnerable to Timbersaw's skills.
* Timbersaw can easily escape from Phantom Assassin thanks to his Timber Chain.
Additional:
* Reactive Armor helps Timbersaw sustain harassment from Stifling Dagger.
* Phantom Assassin has a moderate health pool and usually appears in the front line of battle, making her vulnerable to Timbersaw's magic burst.
* Timbersaw can easily escape from Phantom Assassin thanks to his Timber Chain.

* Phantom Strike's extra attack speed causes Phantom Assassin to proc Counter Helix more often. Using it on Axe also makes Phantom Assassin an easy target for a counter-initiation with Berserker's Call and Blade Mail.
* Most of Axe's abilities pierce Black King Bar, allowing him to lock down Phantom Assassin at any time.
* Berserker's Call greatly reduces Phantom Assassin's ability to crit hard against Axe, and may cause her to kill herself when used with Blade Mail.
Additional:
* Jumping in with Phantom Strike makes Phantom Assassin an exceptionally easy target for Berserker's Call.
* The bonus attack speed from Phantom Strike also means that Phantom Assassin will proc Counter Helix numerous times.
* Black King Bar is generally useless against Axe's abilities and item build, as Black King Bar doesn't prevent Axe from finishing Phantom Assassin off with Culling Blade. It also doesn't work against Berserker's Call and Counter Helix.
* Blade Mail is an item that Axe purchases every game, and it can be used to turn Phantom Assassin's critical strikes against herself. The situation becomes even worse if she's affected by Berserker's Call, as she has no way to stop attacking.

* Axe will destroy her illusions by proccing Counter Helix more often due to him being hit by more attacks.

* Despite her high mobility, Hex or Earth Spike can lock Phantom Assassin down and make her vulnerable.
* Although she has high evasion through Blur, Phantom Assassin has a rather low health pool, making her weak to Lion's magical burst.
Additional:
* Hex and Earth Spike's fast cast animations easily catches Phantom Assassin when she jumps in to attack.
* Finger of Death often ends Phantom Assassin before she can do anything in the early to mid game.

* Both Hex and Mana Drain destroys Naga Siren's illusions in an instant, making it hard to teamfight or push against a team with Lion. If Lion chooses the AoE effect talent for Hex or the multi-target Mana Drain, it can negate her pushing potential entirely.
* Earth Spike is an AoE disable with good damage. If used well, it can help distinguish the true Naga Siren by the damage they take (illusions take more damage).

* Sand King and Phoenix has many tools to deal with a crowd of Heroes, which will work well against a crowd of illusions.

* Phantom Assassin relies on her Blur to stay alive, but is very vulnerable to Sand King's heavy magic damage.
* With Burrowstrike, Sand King can often catch Phantom Assassin before she can use her Black King Bar.
* Sand King can dodge Stifling Dagger with Sandstorm.
* Phantom Assassin has a hard time killing Sand King because of his high mobility.

* While her Phantom Strike does give limited extra attack speed, she cannot use the ability against the Phoenix Sun, and while her Blur may protect her from attacks, Phoenix's strong magical DPS burns away her small health pool quickly, and the attack speed slow makes her unable to fight back (provided she has no source of spell immunity).
Additional:
* Fire Spirits applies a severe attack speed slow, severely hindering Phantom Assassin's damage output. While Phantom Strike may be able to slightly remedy the problem, Phoenix' magical and pure damage output completely ignore Blur's evasion, resulting in severe damage to her low health pool.

* Sand King and Phoenix has many tools to deal with a crowd of Heroes, which will work well against a crowd of illusions.

* Retaliate deals damage to Phantom Assassin for every attack and Stifling Dagger thrown at Centaur.
* Blur cannot evade Double Edge.
Additional:
* Retaliate turns Phantom Assassin's attacks against herself, as he deals damage with every hit taken, and his big health pool makes sure that a lot of hits will be needed.
* If Centaur Warrunner gets the jump on Phantom Assassin first, she will be unable to activate Black King Bar and might be burst down with the help of his Double Edge.
* Stampede can save an ally under attack by Phantom Assassin, offsetting the slow from Stifling Dagger. If he owns an Aghanim's Scepter, he can prevent a low-health ally from being killed in one crit.

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

* Any heroes with low mana pools will die quickly or even instantly to Sanity's Eclipse: Doom, Phantom Assassin, Troll Warlord.

* Sanity's Eclipse will likely instantly kill all illusions.

* Heroes with magical burst damage can often kill Phantom Assassin before she gets to do much: Necrophos, Nyx Assassin, Gyrocopter.

* Flak Cannon and Call Down can easily clear Naga Siren's illusions.

* Since Life drain takes out illusions instantly, Pugna with a scepter is decent versus plenty of illusion heroes, most notably Naga Siren and Terrorblade and the aforementioned Chaos Knight. Phantom Lancer is an exception.

* Ethereal state disarms the target and makes them more vulnerable to magic damage, both of which Phantom Assassin despises. Especially Pugna and any hero that is wielding Ethereal Blade, such as Mirana, Nyx Assassin or Morphling.

* Heroes that rely on escapes to stay alive can be caught and locked down for a long time: Queen of Pain, Phantom Assassin

* Heroes with long-lasting, undispellable debuffs will pinpoint the true Naga Siren: Spirit Breaker, Bloodseeker.

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

Additional:
* High armor thanks to Dragon Blood makes it difficult for Phantom Assassin to burst down Dragon Knight, as she deals 100% physical damage.
* Dragon Tail stuns Phantom Assassin as soon as she initiates, preventing her from gaining bonus attack speed.
* Dragon Knight is one of the few heroes who can safely solo lane against Phantom Assassin alongside a support.

* Cleave heroes will clear her illusions. Such heroes include Sven, Magnus, Dragon Knight in Elder Dragon Form, Ember Spirit (via item), Phantom Assassin (via talent or item), etc.

* Phantom Assassin's single target abilities make her very helpless against swarms of spiderlings.
* Because Phantom Assassin is always reliant on critical strikes, Broodmother will usually have enough time to use Spin Web to save herself.
* Aside from Spin Web, Incapacitating Bite can cripple her due to being reliant on physical attacks and critical strikes.
Additional:
* Phantom Assassin's single target abilities make her very helpless against swarms of Spiderlings.
* Because Phantom Assassin is always reliant on critical strikes, Broodmother will usually have enough time to use Spin Web to save herself.
* Incapacitating Bite cripples her due to reliant on physical attacks.

* Zeus' abilities deal high amounts of burst magical damage, which ignores Naga Siren's high armor.
* Zeus' Arc Lightning is also a good way to destroy Naga Siren's illusions.

* Black King Bar is useless, since all of the Spectre's abilities go through spell immunity,
* Phantom Assassin's Blur cannot evade Desolate because its damage is a separate damage instance and is applied before the attack hits.
* Spectre's high durability provided by Dispersion and damage block items makes her one of the hardest carries to take down.
Additional:
* Dispersion makes it hard for Phantom Assassin to burst down Spectre while also reflecting back Phantom Assassin's high burst damage against herself.
* Desolate ignores the evasion from Blur.
* Black King Bar is useless against Spectre as all of her skills pierce spell immunity.

* Nightmare and Fiend's Grip can ground Phantom Assassin, who normally blinks around with Phantom Strike, and stop her from outputting damage.
* Phantom Assassin's low health pool early on makes her susceptible to Brain Sap and Fiend's Grip's heavy nuke damage.
Additional:
* Nightmare's lengthy duration prevents Phantom Assassin from finishing off a target enemy hero.
* Fiend's Grip can disable Phantom Assassin, even through spell immunity.

* Phantom Assassin's Blur will be useless if Windranger managed to get Monkey King Bar or Bloodthorn, and other than Stifling Dagger, Phantom Assassin has no abilities that can bypass Windrun.
* Focus Fire can still deal considerable damage despite Blur's evasion due to the increased attack speed.

* Static Link can lower the damage output from Coup de Grace procs, hindering Phantom Assassin's main source of damage.
* Eye of the Storm strikes cannot be evaded by Blur.
Additional:
* Static Link greatly lowers the damage output from Coup de Grace, hindering Phantom Assassin's main source of scaling.
* Eye of the Storm strikes cannot be evaded by Blur.

* Mirror Image's illusions increase Echo Slam's damage.
Additional:
* Strong AoE abilities can clear Naga Siren's illusions, or at least make it easier to distinguish the real one by the damage they take.
* Echo Slam deals more damage against more enemies, which can be devestating against Naga Siren and her illusions.

* Troll Warlord can build a Silver Edge or a Monkey King Bar to completely ignore Blur.
* Whirling Axes (Melee) provides a 60% miss chance, making a Coup de Grace critical strike very hard to land.
* Battle Trance negates Coup de Grace, preventing Troll Warlord from dying to her critical hits.
Additional:
* Whirling Axes (Melee) makes it hard to land a Coup de Grace.
* Troll Warlord often buys Silver Edge and Monkey King Bar, the items that greatly counters Phantom Assassin.
* Battle Trance completely negates Phantom Assassin's large damage output, preventing Troll Warlord from dying easily. The lifesteal also allows Troll Warlord to restore much of his health.

* Mortimer Kisses can make quick work of Naga Siren's illusions.
* Scatterblast and Firesnap Cookie AoE damage are also decent ways to deal with Naga's illusions.

* Phantom Assassin's high physical damage is greatly reduced by Bulwark.
* God's Rebuke has true strike, ignoring the evasion from Blur.

* All of Leshrac's abilities, especially Pulse Nova can easily deal with Naga Siren's illusions.

* Slark's Pounce allows him to close the gap on Phantom Assassin and prevent her from escaping with Phantom Strike.
* As a hero who always goes for the Silver Edge and Abyssal Blade Slark can use it to disable Phantom Assassin and her Blur and Coup de Grace, drastically reducing her damage output and ability to evade attacks, and also preventing her from acting.
* Phantom Assassin's Coup de Grace requires Random Number Generation in order to proc, which gives Slark more than enough time to escape and recover himself.

* Morphling's naturally high armor thanks to his high agility makes it hard for Phantom Assassin to take him down with Coup de Grace.
* Phantom Assassin is vulnerable to magical damage, falling easily to Adaptive Strike + Ethereal Blade combo.
Additional:
* Morphling's high armor serves as a direct counter to Phantom Assassin, causing her attacks to do far less damage. She is also very vulnerable to burst damage, and can be brought down quickly using his Ethereal Blade and Adaptive Strike combo.

* Puck relies mainly on magical burst damage, which Phantom Assassin is most vulnerable against.
* Phase Shift and Illusory Orb disjoint Stifling Dagger, also allowing to kite Phantom Assassin.
* Dream Coil will stun Phantom Assassin if she uses Phantom Strike to blink away.

* Many stacks of Sticky Napalm, combined with Flamebreak and Firefly, allows Batrider to destroy illusions from Mirror Image.
* If Batrider can manage to destroy all illusions from Naga Siren, he will be able to use Flaming Lasso on the real one, and will be able to drag her toward his team, potentially preventing Naga Siren to escape with Song of the Siren.
Additional:
* Many stacks of Sticky Napalm, combined with Flamebreak and Firefly, allows Batrider to destroy illusions from Mirror Image.
* If Batrider can manage to destroy all illusions from Naga Siren, he will be able to use Flaming Lasso on real one, and will be able to drag her toward his team, potentially preventing Naga Siren to escape with Song of the Siren.

* 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.

* Heroes with disables that ignore spell immunity will render Phantom Assassin quite useless in teamfights throughout the game: Enigma, Vengeful Spirit, Doom, Bane, Beastmaster, Pudge.

* Heroes with long cast animations can be continuously interrupted by Battery Assault: Centaur Warrunner, Jakiro, Leshrac, Naga Siren, Underlord.

* Heroes with long-lasting, undispellable debuffs will pinpoint the true Naga Siren: Spirit Breaker, Bloodseeker.

* Ethereal state disarms the target and makes them more vulnerable to magic damage, both of which Phantom Assassin despises. Especially Pugna and any hero that is wielding Ethereal Blade, such as Mirana, Nyx Assassin or Morphling.

* Heroes with disables that ignore spell immunity will render Phantom Assassin quite useless in teamfights throughout the game: Enigma, Vengeful Spirit, Doom, Bane, Beastmaster, Pudge.

* Heroes with disables that ignore spell immunity will render Phantom Assassin quite useless in teamfights throughout the game: Enigma, Vengeful Spirit, Doom, Bane, Beastmaster, Pudge.

* Fate's Edict cripples many heroes who rely on attacks, such as Phantom Assassin, Sven, or Enchantress, without a dispel or a Black King Bar.

* Heroes who depends on illusions and summons: Naga Siren, Terrorblade, Arc Warden,Broodmother.

* In early to mid stage, Silence is also a great way to counter escape oriented heroes such as Anti-Mage, Queen of Pain, and Phantom Assassin to prevent them from escaping, provided that they don't have any basic dispels.

* Ethereal state disarms the target and makes them more vulnerable to magic damage, both of which Phantom Assassin despises. Especially Pugna and any hero that is wielding Ethereal Blade, such as Mirana, Nyx Assassin or Morphling.

* 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.

* 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.

* Heroes with disables that ignore spell immunity will render Phantom Assassin quite useless in teamfights throughout the game: Enigma, Vengeful Spirit, Doom, Bane, Beastmaster, Pudge.

* Heroes with illusions and summons can be hard for Phantom Assassin to deal with, as she lacks any AoE abilities to deal with them: Broodmother, Phantom Lancer, Chaos Knight.

* 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.

* Cleave heroes will clear her illusions. Such heroes include Sven, Magnus, Dragon Knight in Elder Dragon Form, Ember Spirit (via item), Phantom Assassin (via talent or item), etc.

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

* Arcane Bolt's long range and low cooldowns allows Skywrath Mage to severely harass Phantom Assassin in lane.
* Ancient Seal prevents Phantom Assassin from escaping or engaging with Phantom Strike.
* Mystic Flare's heavy magical damage nukes Phantom Assassin down quickly during the early to mid game.

* Avalanche, Toss, and Grab Tree combo makes a short work of Naga Siren's illusions.

* Heroes with high mobility can be prevented from using it to their advantage with Earthbind, even if they pack a dangerous arsenal: Earth Spirit, Ember Spirit, Storm Spirit, Nature's Prophet, Phantom Assassin, Riki, Anti-Mage, Weaver.
* See items and abilities disabled by roots

* Meepo can just mess up Naga Siren entirely: His Earthbind is AoE, which can bind her illusions, his Poof is a powerful AoE nuke and will clear her illusions. He is also 2/3/4 Meepos, not one, so her Ensnare will not work efficiently against him.