* Berserker's Call and Counter Helix allow Axe to kill Shadow Fiend if he stands too close to a creep wave.
* Battle Hunger is very strong against Shadow Fiend in the early game because Shadow Fiend's low attack damage makes it hard for him to get last hits.
* Axe's naturally high strength and health regeneration will be enough to tank a lot of Shadow Fiend's damage in the early game.

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

* Arc Lightning allows Zeus to get farm in lane against Shadow Fiend without coming into the range of his Shadowrazes.
* Lightning Bolt can be used to heavily harass Shadow Fiend when he tries to get a last hit.
* Thundergod's Wrath and Lightning Bolt can be used to detect Shadow Fiend if he tries to escape with Shadow Blade.

* 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.

* Heroes with channeling spells are very easy targets for Jakiro's abilities: Crystal Maiden, Dawnbreaker, Enigma, Pudge, Shadow Fiend, Shadow Shaman, Warlock.

* Jakiro's damage over time abilities can clear Naga Siren's illusions and can hurt real Naga Siren even for the duration of Song of the Siren.
* Naga Siren is not a hero that likes to go for Black King Bar, and that makes her very vulnerable to Jakiro's damage over time in every phase of the game.
Additional:
* Jakiro's damage over time abilities can clear Naga Siren's illusions and can hurt real Naga Siren even for the duration of Song of the Siren.
* Naga Siren is not a hero that likes to go for Black King Bar, and that makes her very vulnerable to Jakiro's damage over time in every phase of the game.

* Charge of Darkness allows Spirit Breaker to gank Shadow Fiend in the early game, preventing him from getting Necromastery stacks.
* Nether Strike and Charge of Darkness can be used to prevent Shadow Fiend from casting Requiem of Souls.

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

* Heroes with high burst damage: Lina, Lion, Luna, Nyx Assassin, Queen of Pain.

* Both Hex and Mana Drain destroy 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 shard for 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).

* Heroes with high burst damage: Lina, Lion, Luna, Nyx Assassin, Queen of Pain.

* Since Naga Siren is not a hero that likes to go for Black King Bar, she is vulnerable to nukers with strong magical damage and big area-of-effect spells in every game more than any other carry heroes: Sand King, Jakiro, Leshrac, Lina, Earthshaker, Zeus.

* Late game heroes are Sven's favourite kind of opponent, such as Anti-Mage, Spectre and Shadow Fiend.

* 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.

* Earthshock prevents Shadow Fiend from escaping after Ursa used his Blink Dagger to get on top of him.
* Overpower and Fury Swipes allow Ursa to quickly kill Shadow Fiend.
* Enrage keeps Ursa alive in a manfight with Shadow Fiend and allows him to stay close, even if Shadow Fiend uses Requiem of Souls.

* Static Link can steal Shadow Fiend's high physical damage output from Necromastery, lowering his damage output, and Static Link cannot be prevented by Black King Bar.
* Plasma Field and Eye of the Storm can melt down Shadow Fiend easily, due to his low health.

* Mirror Image's illusions increase Echo Slam's damage.
Additional:
* Earthshaker's 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.

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

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

* Lucent Beam and Eclipse with ministun talent can be used to cancel Requiem of Souls if Shadow Fiend does not have Black King Bar. Likewise, since Shadow Fiend is prone to buying Blink Dagger, an ill-timed Blink Dagger can give Luna a free chance to counter-initiate with Eclipse.
* Moon Glaives and Lunar Blessing allow Luna to outfarm Shadow Fiend in lane and the high physical damage output they provide her can also help her deal with Shadow Fiend even when he buys Black King Bar in late game.
* A well timed Eclipse will burst and kill Shadow Fiend before he even either initiates or gets a chance to retaliate, especially when equipped with Aghanim's Scepter and Ethereal Blade, this could become even worse for Shadow Fiend if he does not have Black King Bar. But bear in mind however, that smart and skilled Shadow Fiend can buy Wind Waker to counter this issue.
* Even though Shadow Fiend can evade all of Luna's abilities with Shadow Blade, a smart Luna will always buy Dust of Appearance to provide vision on Shadow Fiend to her and her team.
Additional:
* Lucent Beam and Eclipse with ministun talent can be used to cancel Requiem of Souls if Shadow Fiend does not have Black King Bar. Likewise, since Shadow Fiend is prone to buying Blink Dagger, an ill-timed Blink Dagger can give Luna a free chance to counter-initiate with Eclipse.
* Moon Glaives and Lunar Blessing allow Luna to outfarm Shadow Fiend in lane and the high physical damage output they provide her can also help her deal with Shadow Fiend even when he buys Black King Bar in late game.
* A well timed Eclipse will burst and kill Shadow Fiend before he even either initiates or gets a chance to retaliate, especially when equipped with Aghanim's Scepter and Ethereal Blade, this could become even worse for Shadow Fiend if he does not have Black King Bar. But bear in mind however, that smart and skilled Shadow Fiend can buy Wind Waker to counter this issue.
* Even though Shadow Fiend can evade all of Luna's abilities with Shadow Blade, a smart Luna will always buy Dust of Appearance to provide vision on Shadow Fiend to her and her team.

* Luna can easily cancel channeling spells with Lucent Beam and 0.25s Eclipse Lucent Ministun talent for Eclipse, she can also buy Abyssal Blade in case they decide to buy Black King Bar: 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.

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

* Shadow Fiend's lack of mobility and low base health make him an easy target for early ganks.

* Kraken Shell dispels both Shadowraze's damage amplification stacks and Requiem of Soul's damage reduction (provided Tidehunter has taken enough damage).
* Ravage cancels Requiem of Souls if Shadow Fiend isn't protected by Black King Bar.
Additional:
* Kraken Shell dispels the damage amplification stacks of Shadowraze as well as the damage reduction from Requiem of Souls (provided he has taken enough damage).
* Anchor Smash reduces Shadow Fiend's large attack damage, Kraken Shell makes Tidehunter the last target Shadow Fiend wants to attack.
* Ravage can easily cancel Requiem of Souls if Shadow Fiend isn't protected by Black King Bar.

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

* Avalanche and Toss combo makes short work of Mirror Image's illusions.
* Tiny's cleave with Tree Grab and area of effect damage with Tree Volley will easily wipe out illusions.

* 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 from escaping 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 the real one, and will be able to drag her toward his team, potentially preventing Naga Siren from escaping with Song of the Siren.

* Decrepify prevents Shadow Fiend from attacking for its duration, potentially preventing him from getting a kill.
* Nether Ward can do heavy damage to Shadow Fiend if he tries to cast his Requiem of Souls and his Shadowraze.
Additional:
* Decrepify prevents Shadow Fiend from attacking for its duration, potentially preventing him from getting a kill.
* Nether Ward can do heavy damage to Shadow Fiend if he tries to cast his Requiem of Souls or spam Shadowraze.

* Requiem of Souls is easily interrupted by Boundless Strike, due to its long cast time.
* Shadow Fiend's lack of mobility and escape makes him an easy target to ambush with Primal Spring, especially during laning stage.
* Being close means he cannot use all three razes on you before you get your Jingu Mastery stacks.

* Doom has several disable abilities to choose from jungle creeps (e.g. War Stomp, Ensnare) to deal with Shadow Fiend who lacks escape abilities.
* When Doom combines creep abilities with Scorched Earth, Infernal Blade, and Doom, Shadow Fiend most likely will die as he cannot use Shadowraze and Requiem of Souls to protect himself, and also cannot even flee by using Shadow Blade or Blink Dagger.
* Although Shadow Fiend has a high physical damage output, Doom has a large health pool to survive it, meaning Doom's combo with high magical damage output will shutdown Shadow Fiend first.
* Doom usually buys Radiance to improve his damage, making his nuke combo more deadly to Shadow Fiend. The blind also prevents Shadow Fiend from landing his attacks often.

* Timbersaw's innate durability is very hard to deal with as Naga Siren as she relies on sustained damage rather than burst damage. Timbersaw's high Pure Damage and low-cooldown AoE nukes can also destroy Naga Siren's illusions very fast. Timbersaw can also build Lotus Orb reflects Ensnare

* Dragon Tail can be used to cancel Requiem of Souls.
* Breathe Fire reduces Shadow Fiend's damage even further.
* Dragon Knight's high strength and Dragon Blood means that he'll be able to tank Shadow Fiend's right clicks.

* 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 build mana boosting items but have low mana regeneration are especially vulnerable against Mana Break and Mana Void: Timbersaw, Slark, Shadow Fiend, Clinkz, Bristleback Nyx Assassin, Magnus

* Heroes that rely on illusions will suffer against Ion Shell, which kills them very quickly: Phantom Lancer, Chaos Knight, Naga Siren, Meepo.

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

* Squishy core heroes (Shadow Fiend, Sniper, etc)

* 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 with channeling spells because Shadow Fiend has nothing to cancel channeling outside of Requiem of Souls: Bane, Enigma, Pudge, Shadow Shaman, Dawnbreaker, Warlock, Crystal Maiden.

Additional:
* Because Shadow Fiend lacks escaping mechanisms, and is dependent on fair positioning for channeling Requiem of Souls, it's easier for Warlock with his long range crowd control abilities to lock Shadow Fiend down for his team.

* Heroes with channeling spells because Shadow Fiend has nothing to cancel channeling outside of Requiem of Souls: Bane, Enigma, Pudge, Shadow Shaman, Dawnbreaker, Warlock, Crystal Maiden.

* Heroes that are hard to kill without lockdown: Puck, Weaver.

* Heroes with channeling spells because Shadow Fiend has nothing to cancel channeling outside of Requiem of Souls: Bane, Enigma, Pudge, Shadow Shaman, Dawnbreaker, Warlock, Crystal Maiden.

* Since Naga Siren is not a hero that likes to go for Black King Bar, she is vulnerable to nukers with strong magical damage and big area-of-effect spells in every game more than any other carry heroes: Sand King, Jakiro, Leshrac, Lina, Earthshaker, Zeus.

* Illusion heroes will struggle against Primal Beast's area damage capability, such as Chaos Knight, Naga Siren, Terrorblade.

* Heroes that can gank Shadow Fiend in the early game: Earth Spirit, Nyx Assassin, Riki, Spirit Breaker.

* Heroes with channeling spells because Shadow Fiend has nothing to cancel channeling outside of Requiem of Souls: Bane, Enigma, Pudge, Shadow Shaman, Dawnbreaker, Warlock, Crystal Maiden.

* Heroes with channeling spells because Shadow Fiend has nothing to cancel channeling outside of Requiem of Souls: Bane, Enigma, Pudge, Shadow Shaman, Dawnbreaker, Warlock, Crystal Maiden.

* Keeper of the Light can stall pushes with Illuminate. This makes him strong against pushing heroes: Terrorblade Naga siren Nature's Prophet and Anti-Mage

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

* As long as Windranger is able to identify the real hero among the illusions, heroes relying on them can be easily tagged with Focus Fire: Chaos Knight, Terrorblade, Phantom Lancer, Naga Siren.

* Heroes that are hard to kill without lockdown: Puck, Weaver.

* Heroes with long animations can be frequently interrupted with Cold Snap: Earthshaker, Monkey King, Shadow Fiend Lina

* 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 who lack escape mechanisms or disables are all easy targets for Phantom Assassin if they are not careful. Look for Luna, Venomancer, and Shadow Fiend and try to catch them off guard.

* 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 with high burst damage: Lina, Lion, Luna, Nyx Assassin, Queen of Pain.

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

* The blind from Laser prevents Shadow Fiend from attacking for its duration, potentially preventing him from getting a kill.
* Scythe of Vyse can be used to prevent Shadow Fiend from casting Requiem of Souls.
* A combination of Tinker's abilities and his items (like the Dagon 5 and Ethereal Blade combo) can kill Shadow Fiend quickly.
Additional:
* During the laning stage Laser will reduce Shadow Fiend's last hits, preventing him from getting Necromastery souls.
* Shadow Fiend has low health and is vulnerable to Tinker's high magic burst.

* Bounty Hunter can absolutely destroy a Shadow Fiend's game by ganking his midlane with Shadow Walk, Jinada and Shuriken Toss.
* If his lane goes bad, a Shadow Fiend usually goes to the jungle. Follow him with Shadow Walk and take half of his experience.
* Due to its ministun, Shuriken Toss is a good way to interrupt Shadow Fiend's long cast animation on Requiem of Souls.
Additional:
* Shuriken Toss can be used to cancel Requiem of Souls.
* Shadow Walk and Jinada allow Bounty Hunter to gank Shadow Fiend early on
* Track prevents Shadow Fiend from escaping with Shadow Blade.

* Shadow Fiend, a normal Shadow Blade builder often relies on its invisibility to escape fights. Corrosive Haze reveals Shadow Fiend and also weakens his already low armor.

* Blade Fury offers good AoE damage to clear illusions and can hurt the real Naga Siren as well if she chooses to blend in the illusions. Diffusal Blade does nothing to Juggernaut either when he uses Blade Fury.
* Aghanim's Shard upgraded Blade Fury along with Lv 20 DPS talent will shred all illusions almost instantly, especially when combined with Mjollnir, a common item for Juggernaut.

* Glimpse and Kinetic Field allows Disruptor to set up some early kills onto Shadow Fiend.
* Static Storm can be used to cancel the cast of Requiem of Souls.

* Enfeeble can be used to decrease Shadow Fiend's already abysmal level one damage even further, preventing him from getting farm and Necromastery stacks.
* Brain Sap allows Bane to heavily harass Shadow Fiend.
* Nightmare allows Bane to set up some early ganks onto Shadow Fiend.
* Fiend's Grip enables Bane to completely take Shadow Fiend out of a fight and potentially even kill him, even through Black King Bar.
Additional:
* Enfeeble can be used to decrease Shadow Fiend's already abysmal level one damage even further, preventing him from getting farm and Necromastery stacks.
* Brain Sap allows Bane to heavily harass Shadow Fiend.
* Nightmare allows Bane to set up some early ganks onto Shadow Fiend.
* Fiend's Grip enables Bane to completely take Shadow Fiend out of a fight and potentially even kill him, even through Black King Bar.

* Medusa's Split Shot will whittle down all of Naga Siren's illusions, including Naga Siren herself.

* The Reflection of Shadow Fiend cause Presence of the Dark Lord to affect Shadow Fiend, reducing his armor and making it easier for Terrorblade to kill him. Shadow Fiend also doesn't have lots of survivability or control abilities in order to escape.
* If Shadow Fiend chooses to go for a physical damage item build, he'll have a hard time against Terrorblade's high armor.

* Heroes who depend on attacks (such as Shadow Fiend or Drow Ranger) can be nullified by Fire Spirits' attack speed slow.

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