* Mirror Image can be effective since Night Stalker cannot withstand fighting Illusions. If he's unable to tell which Naga Siren is real, he will have a hard time landing his Void and Crippling Fear.
Additional:
* Ensnare and Song of the Siren prevents Night Stalker from escaping and ganking during daytime or even nighttime.
* Rip Tide reduces Night Stalker's armor, making him easier to focus down.
* Mirror Image can be effective against Night Stalker, due to his single target abilities.

* Whirling Axes (Melee) provides a 60% miss chance, which can make the attack speed bonus from Hunter in the Night largely ineffective.
* Berserker's Rage together with Battle Trance and Fervor stacks gives him a high chance of rooting Night Stalker, which allows Troll Warlord to man-fight Night Stalker in any stage of the game, regardless of whether or not it's night.

* Heroes with illusions: Chaos Knight, Naga Siren, Phantom Lancer

* The passive armor provided by Berserker's Rage makes Troll Warlord resilient to Feast in early game.
* The 60% miss chance given by Whirling Axes (Melee) is useful when Rage is not active.
* Battle Trance can purge Open Wounds, negating a large amount of Lifestealer's sustain in fights.

* Mirror Image can cause Huskar to Life Break the wrong target.
* Rip Tide reduces Huskar's already low armor.
* Song of the Siren allows teams to recover from Huskar's initiation, as well as the damage over time from Burning Spears.

* Carries that can out damage Huskar will do well against him: Legion Commander, Faceless Void, Troll Warlord, Phantom Assassin.

Additional:
* Whirling Axes (Melee) provides a 60% miss chance, resulting in Huskar's attacks missing a lot of the time if it isn't dispelled.
* Troll Warlord's Fervor ramps up in a very similar way as Huskar's Berserker's Blood: as soon as Huskar has high enough health regeneration, Troll Warlord has a high enough attack speed to negate it.

* Troll Warlord's ability to attack as a ranged hero allows him to destroy Juggernaut's Healing Ward from afar.
* Battle Trance, when activated during Omnislash, allows Troll Warlord to survive the full duration of Omnislash and retaliate once it is over.

* Illusion-based heroes are effective against Omnislash and Juggernaut's single-targeted damage: Naga Siren, Chaos Knight, Terrorblade,Phantom Lancer.

* Mobility heroes will often be rooted by Troll Warlord and unable to escape, like Storm Spirit.

* Any hero reliant of mobility, like Storm Spirit.

* Naga Siren is a natural split-pusher. With a Radiance equipped, she will easily out-push Nature's Prophet, farming his treants in the process.
* Ensnare prevents Teleportation. Even if he hid inside Sprout, Song of the Siren lasts long enough to prevent him from escaping.
Additional:
* Naga Siren is a natural split-pusher. With Rip Tide, she will easily out-push Nature's Prophet, farming his treants in the process.
* Ensnare prevents Teleportation. Even if he hides inside Sprout, Song of the Siren lasts long enough to prevent him from escaping.

* Battle Trance and Fervor can help cancel out Untouchable.
Additional:
* Untouchable's attack speed slow is easily remedied by Fervor stacks and Battle Trance.
* Troll Warlord is a natural Silver Edge carrier, disabling Enchantress' Untouchable.

* Song of the Siren is very difficult for Rubick to Spell Steal when he is affected by sleep.
* Ensnare and Rip Tide together with some attacks can take Rubick down quickly, due to his low health pool and armor.
* Naga Siren usually buys Diffusal Blade, which will prevent Rubick from spamming his abilities from Spell Steal.
* Mirror Image allows to dodge the incoming stun from Telekinesis (when she is not a target) and it can also to dodge and dispel Fade Bolt's damage reduction debuff.

* Troll Warlord's passive root, high attack speed, and blind from Whirling Axes makes him an exceedingly difficult opponent for Anti-Mage to take down in a one-on-one fight.
* Troll Warlord's low mana causes him to take little damage from Mana Void.
Additional:
* Whirling Axes (Melee) provides a 60% miss chance, preventing Anti-Mage from burning Troll Warlord's small mana pool.
* Troll Warlord's passive root allows him to very effectively fight an Anti-Mage by preventing Anti-Mage from Blinking away. This is even more effective when combined with a Skull Basher or Abyssal Blade.
* Counterspell will do nothing to prevent Troll Warlord's high physical damage.
* Due to Troll Warlord's abysmal base intelligence and intelligence gain, he is one of the worst targets to use Mana Void on.

* Mirror Image's illusions can easily walk straight at Dazzle and attack him, due to Dazzle's lack of reliable AoE nukes or disables.
* Ensnare roots Dazzle or his allies, making it harder to stay range of Dazzle's saving abilities.
* Song of the Siren can be used to initiate a fight with superior positioning, potentially zoning Dazzle's high-impact spells out of the fight.

* Song of the Siren lasts long enough to prevent a successful Duel (but only if Naga wasn't the target).

* Troll Warlord's melee bash and high attack speed can often help him and his allies win Duels against Legion Commander.

* Due to Fervor and Battle Trance, Troll Warlord has a significant attack speed, enabling him to crush Tombstone quickly.
* Undying usually stays at the front line with no disables, making him an easy target for Troll Warlord.

* Ensnare is good vs bear.
* In teamfights, song of the siren may be used to properly set up and coordinate an attack on Lone Druid in the backline, bursting him down, allowing to completely ignore the bear.
* Druid lack innate AoE capabilities giving him no good way of dealing with illusions.

* Song of the Siren stops him from acting and her illusions can push better than him because Mirror Image has a longer duration.
* Arc Warden does not often build Radiance, which is useful for illusions and countering illusion pushes.
* Mirror Image dispels Flux or prevents Flux's slow.
Additional:
* Her illusions can push better than Arc Warden's Tempest Double because Mirror Image has a longer duration.
* Mirror Image dispels Flux, and the illusions stop Flux from working.

* Song of the Siren completely wastes Abaddon Borrowed Time while keeping him in place.
* Naga Siren is able to simply dispel Abaddon's Curse of Avernus with Mirror Image before getting hit 4 times consecutively.
* Although Naga Siren's illusions can be easily destroyed by Aphotic Shield, Naga Siren can resolve that issue easily by purchasing Heart of Tarrasque to drastically increase her tankiness. Plus, the said item makes Naga Siren harder to be distinguished from her illusions.

* Heroes that build Diffusal Blade or can fit it well into their item build will also make Medusa much less tanky: Riki, Naga Siren, Terrorblade, Juggernaut, Spectre, Slark,Drow Ranger.

* Any hero who can counter-initiate in anticipation without getting caught in Reverse Polarity: Sven, Omniknight, Enigma, Luna, Naga Siren, Mars, Jakiro, Venomancer, Elder Titan, Faceless Void, Rubick, Keeper of the Light, Pugna, Invoker, Spectre, Alchemist, Treant Protector, Lina, Oracle, Zeus, Shadow Shaman, Phoenix, Razor, Huskar, Batrider, Kunkka, Tidehunter, Wraith King, Sand King.

* Any hero who can survive Magnus's initiations and manfight him: Huskar, Faceless Void, Weaver, Abaddon, Troll Warlord, Alchemist, Dragon Knight, Night Stalker, Viper.

* Heroes that rely on right-clicks will find that their attacks will miss a lot, due to Whirling Axes (Melee)'s miss chance. Such heroes include Phantom Assassin, Terrorblade, and Morphling.

* Heroes that rely on right-clicks will find that their attacks will miss a lot, due to Whirling Axes (Melee)'s miss chance. Such heroes include Phantom Assassin, Terrorblade, and Morphling.

* Illusion and heroes with summons are difficult to kill with Chen's single-target offensive spells: Terrorblade, Phantom Lancer, Chaos Knight, Broodmother, Naga Siren, Lycan, Visage. However, Chen can convert enemy summons with Holy Persuasion, as long as they don't bunch up.

Additional:
* Naga Siren can make landing Chen's combo very hard due to her being an illusion hero.
* Ensnare will prevent Chen from activating Hand of God.

* Heroes with summons like Broodmother,Enigma, Invoker, Nature's Prophet, Lycan, Visage;or illusions, like Naga Siren, Phantom Lancer, Terrorblade are effective at keeping the choke points and rune spawns safe from Proximity mines in the early game.

* Illusion heroes like the aforementioned Phantom Lancer or Naga Siren, or heroes that tend to buy Manta Style, like Luna or Juggernaut, will give Slardar a hard time, as his damage is single-targeted.

* Illusion heroes, such as Naga Siren, Phantom Lancer, Chaos Knight, Terrorblade will become strong against Tinker in the late game when Tinker's only area of effect damage, March of the Machines, ceases to kill illusions quickly. Without Aghanim's Scepter Tinker is forced to defensively disarm heroes with Laser, leaving illusions free to deal physical damage which Tinker's low armor makes highly effective. In addition, Mjollnir or Battle Fury, two common pickups against illusion heroes, don't work well on Tinker at all.

* Illusions make it difficult for Necrophos to target his Reaper's Scythe correctly, thus giving illusion heroes like Chaos Knight or Naga Siren an edge against Necrophos.

* Heroes that create illusions (such as Spectre, Shadow Demon, Phantom Lancer, Naga Siren, Chaos Knight, Terrorblade) or bring other units into the fight (such as Nature's Prophet, Lone Druid, Chen, Enchantress and the aforementioned Meepo and Arc Warden) can cause Eclipse to strike the illusions/summons unintentionally. (However, in many cases Moon Glaives can resolve this issue and eliminate them before activating Eclipse).

* Naga Siren with Mirror Image
* Heroes that can dodge Glimpse:
* Puck with Phase Shift
* Riki with Tricks of the Trade
* Phantom Lancer with Doppelganger
* Ember Spirit with Sleight of Fist and Activate Fire Remnant
* Chaos Knight with Phantasm
* Naga Siren with Mirror Image
* Tusk with Snowball
* Juggernaut with Omnislash
* Brewmaster with Primal Split
* Lifestealer with Infest
* Phoenix with Supernova

* Mirror Image can dispel Frostbite.
* Song of the Siren can stop Freezing Field regardless of any kind of invisibility as well as allow Naga Siren's team to quickly close the gap on Crystal Maiden.
Additional:
* Mirror Image can dispel Frostbite.
* Ensnare and Song of the Siren can stop Freezing Field.
* Song of the Siren can allow her team to quickly close the gap on Crystal Maiden.

* Heroes with a low attack speed or are fragile will find themselves unable to deal with Troll Warlord's high physical damage and attack speed, like Crystal Maiden or Sven.

* 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.
* 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), Pugna

Additional:
* Ensnare disables Lanaya's invisibility and Blink Dagger (a core item on Templar Assassin), and her illusions will break Refraction easily.

* Naga Siren with Mirror Image
* Heroes that can remove the Track debuff with their skills:
* Abaddon with Aphotic Shield and Borrowed Time
* Huskar with Life Break
* Juggernaut with Blade Fury
* Legion Commander with Press the Attack
* Lifestealer with Rage and Infest
* Naga Siren with Mirror Image
* Omniknight with Heavenly Grace
* Oracle with Fortune's End and False Promise
* Phantom Lancer with Doppelganger
* Slark with Dark Pact
* Ursa with Enrage
* Weaver with Time Lapse
* Tidehunter with Kraken Shell when damage received reaches the threshold.

Additional:
* Bounty Hunter is a single target dealer, so he will not fare well against Naga Siren. He might as well try to Track her, but her Mirror Image will dispel the effect. Also, Ensnare reveals invisible units while they're rooted, putting Bounty Hunter in a tricky situation.

* Heroes with summons and illusions such as Broodmother and Naga Siren, are ill-suited for Wraith King to fight, as he has no source of waveclear.

* Lycan is a carrier built entirely with physical attacks, having 0 AoE presence and no spell power. Due to this, he can't deal with illusions or Naga Siren's Ensnare.

* Whirling Axes (Melee)'s blind makes Sven nearly useless in the early game and allows Troll Warlord to him on comfortably.
* Battle Trance will mean Sven will never take Troll out in a 1vs1 with equal farm.
Additional:
* Berserker's Rage together with Troll Warlord's high attack speed gives Troll a high chance of rooting enemies, which allows Troll Warlord to man-fight Sven.
* Whirling Axes (Melee) provides a 60% miss chance, and the passive armor provided by Berserker's Rage makes Troll resilient to physical damage in early game. Sven's God's Strength is much less effective as a result.
* Beware that Sven can farm much faster than Troll Warlord by stacking ancients and clearing them with Great Cleave.

* 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.

* Naga Siren can easily disjoint, and dispel Corrosive Skin with Mirror Image.
* Since Viper is a single-target hero, he will not stand a chance against Naga Siren because she is an illusion based hero.

* Ensnare with her attacks allows Naga Siren to gank Sniper easily.
* Rip Tide removes Sniper's very little armor.

* Song of the Siren can be used to time out Guardian Angel, giving Naga Siren's team an easy opportunity to counter-initiate.
Additional:
* Song of the Siren will waste Guardian Angel.
* Ensnare fully works on Heavenly Graced targets. However, Ensnare is dispellable with any dispel, and so can be dispelled by Heavenly Grace.
* As an agility hero that relies on illusions, Naga is one of the most natural Diffusal Blade carriers, the bane of every hero with a small mana pool.

* Berserker's Rage will repeatedly trap Bloodseeker in a one-on-one fight.
* Whirling Axes (Melee) blinds Bloodseeker, causing him to miss 60% of the time, and therefore reduces his ability to gain the upper hand in teamfights.

* Due to Fervor and Battle Trance, Troll Warlord is one of the best heroes to deal with Supernova.

* Troll Warlord can root and deal a lot of damage to a single Meepo while lifestealing through the assault from the other Meepos. Meepo needs expensive items like Ethereal Blade or Heaven's Halberd to be able to fight him.

* Heroes with powerful rooting abilities will disable most of Pangolier's skill, a bonus point if it pierce spell immunity since it will also be able to stop Pangolier during his Rolling Thunder: Treant Protector, Meepo, Crystal Maiden, Dark Willow, Underlord, Naga Siren

* Song of the Siren can be used to nullify the effects of Winter's Curse, and when upgraded with Aghanim's Scepter it also outmatches the heal of Cold Embrace.
* If Winter Wyvern is reckless enough to put an ally in Cold Embrace, Naga Siren will be able to use her Ensnare to extend the disable on the hero affected by Cold Embrace.