* Strafe, Tar Bomb and Burning Barrage from Aghanim's Shard allow Clinkz to quickly kill Io due to its low armor.
* Clinkz iz a hero that very often goes for Orchid Malevolence, and its upgrade Bloodthorn. Alternatively, Clinkz also loves to buy Gleipnir. And if Clinkz has both of them, he will be able to root and silence Io and prevent him from escaping with either Tether or Relocate.

* Ember Spirit's Flame Guard provides no protection against Clinkz's physical damage output.
* Ember Spirit's low armor and health make him easy to kill quickly if a teammate can hold him down.
* If Clinkz has farmed an item that can disable, he can sneak up to and hunt down Ember Spirit while he farms or split pushes alone.

* Batrider's Flaming Lasso can be used to cancel Io's attempts to escape with Relocate and drag him away from his Tethered target. And since Io doesn't like buying Linken's Sphere, he will be always vulnerable to Batrider's initiations.
* Io's tendency to stick close to it's Tethered target can make Io and it's target vulnerable to Batrider's harrasing.
* Aghanim's Scepter upgraded Flaming Lasso allows Batrider to catch and drag two heroes at once, not just one. Which can potentially turn Io's Tether against him.
Additional:
* Batrider's Flaming Lasso can be used to cancel Io's attempts to escape with Relocate and drag him away from his Tethered target. And since Io doesn't like buying Linken's Sphere, he will be always vulnerable to Batrider's initiations.
* Io's tendency to stick close to it's Tethered target can make Io and it's target vulnerable to Batrider's harrasing.
* Aghanim's Scepter upgraded Flaming Lasso allows Batrider to catch and drag two heroes at once, not just one. Which can potentially turn Io's Tether against him.

* Batrider has huge damage from his Sticky Napalm and hand strikes on the target, with this effect. And Ember Spirit not only has a small reserve of health, but also has a melee type of attack. If these two collide on the center line, then Ember Spirit will have to finish off several creeps from afar with a Sleight of Fist, otherwise he will lose a lot of health from long-range Batrider attacks under Sticky Napalm, and possibly even kill, because Ember Spirit does not have the ability to interrupt Batraider with his damage if he decides to attack
* Ember Spirit is a very tasty target for Flaming Lasso, because it has a small reserve of health, and all the power lies in the abilities that Flaming Lasso forbids using, this can help the Batraider team quickly deal with the unpleasant "jumping" Ember Spirit in a fight if he gets into Flaming Lasso
Additional:
* Batrider has huge damage from his Sticky Napalm and hand strikes on the target, with this effect. And Ember Spirit not only has a small reserve of health, but also has a melee type of attack. If these two collide on the center line, then Ember Spirit will have to finish off several creeps from afar with a Sleight of Fist, otherwise he will lose a lot of health from long-range Batrider attacks under Sticky Napalm, and possibly even kill, because Ember Spirit does not have the ability to interrupt Batraider with his damage if he decides to attack
* Ember Spirit is a very tasty target for Flaming Lasso, because it has a small reserve of health, and all the power lies in the abilities that Flaming Lasso forbids using, this can help the Batraider team quickly deal with the unpleasant "jumping" Ember Spirit in a fight if he gets into Flaming Lasso

* Heroes whose abilities can affect multiple enemies at once: Dawnbreaker, Ember Spirit, Lina, Luna, Jakiro, Leshrac, Invoker, Muerta, Dazzle.

* Ember Spirit has a small mana pool, which is why QW-Invoker can burn it out very effectively with his own E.M.P., do not give Ember Spirit the opportunity to play with his abilities and cause damage with them in a fight.
* QW-Invoker Destroys Ember Spirit's Flame Guard with his own Tornado, which is why Ember Spirit cannot defend against Invoker's strong magic damage.
Additional:
* Ember Spirit has a small mana pool, which is why QW-Invoker can burn it out very effectively with his own E.M.P., do not give Ember Spirit the opportunity to play with his abilities and cause damage with them in a fight.
* QW-Invoker Destroys Ember Spirit's Flame Guard with his own Tornado, which is why Ember Spirit cannot defend against Invoker's strong magic damage.

* Heroes with the ability to heal allies will not be able to heal heroes affected by Doom: Chen, Dazzle, Io, Oracle, Omniknight, Witch Doctor, Winter Wyvern, Abaddon, etc.

* Ember Spirit cannot use his Activate Fire Remnant to escape while affected by Doom.

* Heroes with both illusions and summons, for Io has nothing to deal with multiple enemies at once outside from Spirits's weak area-of-effect: Beastmaster, Broodmother, Chaos Knight, Lycan, Naga Siren, Nature's Prophet, Phantom Lancer, Shadow Shaman, Terrorblade, Visage, Warlock, Wraith King.

* Heroes who rely on high mobility are especially vulnerable to Primal Roar: Storm Spirit, Ember Spirit, Queen of Pain.

* The pure damage provided by Purification is a great addition for killing Ember Spirit, as well as a good way of saving teammates.
* Guardian Angel will temporarily save his allies from Sleight of Fist's physical damage, and Ember Spirit is not a hero that will get Orchid Malevolence to counter it.

* Oracle can shut down both of Ember's early game abilities. Fortune's End can dispel Flame Guard on Ember Spirit and Searing Chains on allies.
* When Ember Spirit is affected by Fortune's End, his Fire Remnants move at 0 movement speed.
* Disarming him with Fate's Edict does affect Ember's Sleight of Fist ability, possibly making him useless for a few seconds in the late game without a dispel or spell immunity. This is especially good if he has a rapier or two. However, positioning for this is difficult when Ember plays far back.

* Living Armor and Leech Seed can be used to save a hero from a Relocate gank.
* Overgrowth can be used to cancel escape attempts with Relocate.
* Once Treant Protector buys Aghanim's Scepter, he will gain access to Eyes in the Forest, that will allow him to enchant a tree which will grant him unobstructed vision in that location, allowing him to keep his allies alerted on Io and his Tethered's attempts to gank them, and which can also allow Overgrowth to damage them and root them if they are within a 800 radius of an tree affected by Eyes in the Forest.

* Cold Embrace can render the extra attack speed from Overcharge meaningless.
* Splinter Blast and Winter's Curse are very affective against Io, as it has to stay close to his Tethered target.

* Lone Druid becomes unkillable and impenetrable for Ember Spirit on the central line, as it has a huge reserve of health from the Summon Spirit Bear and a large regeneration from Spirit Link, which is why Sleight of Fist practically does not break through either one or the other on the line, and Lone Druid at this time can easily expel Ember Spirit from the line, push and gain gold and level
* Entangling Claws and Savage Roar abilities completely disable Ember Spirit's ability to dodge abilities or get out of an unpleasant fight for him on Fire Remnant, which can give the Lone Druid team the opportunity to kill him
Additional:
* Lone Druid becomes unkillable and impenetrable for Ember Spirit on the central line, as it has a huge reserve of health from the Summon Spirit Bear and a large regeneration from Spirit Link, which is why Sleight of Fist practically does not break through either one or the other on the line, and Lone Druid at this time can easily expel Ember Spirit from the line, push and gain gold and level
* Entangling Claws and Savage Roar abilities completely disable Ember Spirit's ability to dodge abilities or get out of an unpleasant fight for him on Fire Remnant, which can give the Lone Druid team the opportunity to kill him

* Lich's Chain Frost forces Io to either give up providing buff to his ally with Tether or suffer devastating damage with his Tethered ally.
* Lich can easily use Sinister Gaze to disable Io from getting away with Tether or Relocate.

* The pure damage provided by Arcane Orb is a great addition for killing Ember Spirit.
* Astral Imprisonment fully negates all magic damage of Flame Guard and Searing Chains and will temporarily save himself from Sleight of Fist's physical damage, and Ember Spirit is not a hero that can counter these skills.

* Using X Marks the spot Kunkka can prevent Ember Spirit from escaping with Activate Fire Remnant, until he purchase Eul's Scepter of Divinity or Linken's Sphere.

* Fireblast is a good tool to interrupt Io during its escapes through Tether.
* Ignite can be one of the few spells with enough total damage to out-trade the sustained healing Io provides for its fellow laner.
* However, picking other supports that focus less on the laning phase is generally a better choice against Io.

* Phantom Strike allows Phantom Assassin jump directly to Io.
* Coup de Grace can make a short work of Io's low health and armor.

* Io is a hero who needs to be close to it's tethered target to make it effective, and that's where Leshrac gets the advantage thanks to many of his area-of-effect abilities.
* Lightning Storm will usually hit both Io and its tethered target since both will be close enough for the lightning to jump.
* Diabolic Edict and Pulse Nova hit all units near Leshrac, meaning he can do colossal damage to both, Io and its tethered target.
Additional:
* Lightning Storm will usually hit both Io and his Tethered target since both will be close enough for the lightning to jump. It can then be followed up by Split Earth.
* Diabolic Edict and Pulse Nova hit all units near Leshrac, meaning he can do colossal damage to Io and his Tethered target.

* Ice Blast prevents Io from healing an ally with Tether and prevents healing from Overcharge
* Io is a common Mekansm builder which is useless if he is affected by Ice Blast.
Additional:
* Ice Blast prevents Io from healing the target.
* Ancient Apparition can easily harass Io on lane with Chilling Touch due to it's high range and damage. This can get even worse if Ancient Apparition buys Aghanim's Scepter and combines it with items that can give him bonus attack damage and attack speed.
* Chilling Touch combined with Ice Vortex makes it nearly impossible for Io to escape from Cold Feet. Ice Vortex can also make Io and it's tethered target more vulnerable to Ancient Apparition and his allies's magical damage.

* Heroes with either magical, physical or pure damage burst: Bane, Ember Spirit, Leshrac, Lina, Luna, Nyx Assassin, Phantom Assassin, Skywrath Mage, Tinker, Ursa, Void Spirit.

* With Vendetta, Nyx Assassin can move closely to Ember Spirit when he's farming with his Flame Guard and use Spiked Carapace with Impale to provide a reliable and long disable.
Additional:
* Spiked Carapace can be easily triggered by Flame Guard or Battle Fury, setting up a deadly Impale.

* Global Silence and Last Word can prevent Ember Spirit from casting Activate Fire Remnant to escape.
* Glaives of Wisdom also provide high pure damage that is not negated by Flame Guard.
* Arcane Curse is also a potent harassing tool in the laneing stage as its cooldown is lower than Flame Guard's.

* Shadowraze can easily remove the protection from Flame Guard and kill Ember Spirit due to his low health.
* Ember Spirit is very vulnerable to physical damage from Necromastery.

* Lucent Beam can be used to cancel both, Tether and Relocate.
* Like with Leshrac's Diabolic Edict, Lightning Storm and Pulse Nova abilities. Luna's Moon Glaives and Eclipse abilities can make short work of Io and its tethered ally, particularly when upgraded with Aghanim's Scepter.
Additional:
* Lucent Beam and 0.25s Eclipse Lucent Ministun talent for Eclipse can be used to cancel both, Tether and Relocate.
* Luna's Moon Glaives and Eclipse abilities can make short work of Io and its tethered ally, particularly when upgraded with Aghanim's Scepter.

* Faceless Void is one of the best heroes against Ember Spirit, providing a lot of ways of dealing with him. Ember Spirit becomes a lot weaker if affected by Time Dilation, as he can no longer spam Sleight of Fist.
* Chronosphere is also a reliable lockdown for Ember Spirit, although it can be evaded sometimes by Activate Fire Remnant. Additionally, Void can easily negate Sleight of Fist damage with Time Walk.
* And finally, Void is a great Diffusal Blade carrier. Not only Manabreak's physical damage not negated by Flame Guard, but it also burns Ember Spirit's mana. That, in turn, prevents him from escaping if he survived Chronosphere.

* Huskar can destroy Ember Spirit both on the line and in the game. It will be extremely difficult for Ember Spirit to finish off the creeps, because Huskar will not let him approach them, and if Ember Spirit does come up, Huskar just shuts him up with his Burning Spear and Ember Spirit will have to go to the base or bring himself treatment, or continue to stand and die. In all cases, Ember Spirit will go into negative
Additional:
* Ember Spirit does minimal damage to Huskar until the very late game.
* Huskar can destroy Ember Spirit both on the line and in the game. It will be extremely difficult for Ember Spirit to finish off the creeps, because Huskar will not let him approach them, and if Ember Spirit does come up, Huskar just shuts him up with his Burning Spear and Ember Spirit will have to go to the base or bring himself treatment, or continue to stand and die. In all cases, Ember Spirit will go into negative

* Lion possesses two strong disables in Earth Spike and Hex and heavy magic burst with Finger of Death which help lock him down and prevent him from escaping with Activate Fire Remnant. When getting his Blink Dagger Lion can punish Ember Spirit's overextension immediately, or initiate a fight on him with disables.

* Poison Touch allows Dazzle to harass both, Io and it's tethered target on lane. Aghanim's Shard upgraded Poison Touch can also hex both, Io and it's tethered target, preventing them from escaping with Relocate, and also disarming them, silencing them, muting them and rendering them helpless against Dazzle and his allies.
* Io's damage output is one of the weakest, therefore Dazzle will have plenty of time to save an ally with Shallow Grave from gank by Io and it's tethered target.
* Shadow Wave will always hit both, Io and it's tethered target if they are near the ally Dazzle uses Shadow Wave on, while healing Dazzle's allies near them. Aghanim's Scepter upgraded Shadow Wave can bounce on both, Io and it's tethered target, causing them both to take damage and to be attacked by Dazzle. And unlike Io who doesn't get healed while using Tether, Shadow Wave will always heal Dazzle no matter on which of his allies he uses it on.
* Bad Juju will cause both, Io and it's tethered target to lose armor every time Dazzle casts a spell while strengthening armor of Dazzle's allies.
Additional:
* Poison Touch allows Dazzle to harass both, Io and it's Tethered target on lane. Aghanim's Shard upgraded Poison Touch can also hex both, Io and it's Tethered target, preventing them from escaping with Relocate, and also disarming them, silencing them, muting them and rendering them helpless against Dazzle and his allies.
* Io's damage output is one of the weakest, therefore Dazzle will have plenty of time to save an ally with Shallow Grave from gank by Io and it's Tethered target.
* Shadow Wave will always hit both, Io and it's Tethered target if they are near the ally Dazzle uses Shadow Wave on, while healing Dazzle's allies near them. Aghanim's Scepter upgraded Shadow Wave allows Dazzle Shadow Wave directly on Io and it's Tethered target which can also bounce on both, Io and it's tethered target, causing them both to take damage and to be attacked by Dazzle. And unlike Io who doesn't get healed while using Tether, Shadow Wave will always heal Dazzle no matter on which of his allies he uses it on.
* Bad Juju will cause both, Io and it's tethered target to lose armor every time Dazzle casts a spell while strengthening armor of Dazzle's allies.

* Quill Spray is very effective against Io, as it has very low armor and has to stay close to the fight to not break its Tether.

* Soulbind can target both Io and its Tethered ally, allowing Grimstroke and his team to target both with single target spells. Should Io try to Relocate, Phantom's Embrace can stop its channel to prevent escape.
Additional:
* Grimstroke can catch Io and his Tethered ally easily with Soulbind as Io has a tendency to Tether himself with an ally frequently, which also makes them easier targets for Soulbind.
* Io is highly vulnerable to disables. Hence, Grimstroke's Phantom's Embrace is a great ability to hinder Io's potential.

* Impetus will deal huge amounts of damage when he uses a Fire Remnant to escape.
* Flame Guard is useless against Impetus as it deals Pure damage.
* Enchant can be used to dispel Flame Guard.

* Heroes with either magical, physical or pure damage burst: Bane, Ember Spirit, Leshrac, Lina, Luna, Nyx Assassin, Phantom Assassin, Skywrath Mage, Tinker, Ursa, Void Spirit.

* Heroes with either magical, physical or pure damage burst: Bane, Ember Spirit, Leshrac, Lina, Luna, Nyx Assassin, Phantom Assassin, Skywrath Mage, Tinker, Ursa, Void Spirit.

* Heroes that are hard to gank: Axe, Death Prophet, Phantom Lancer, Slark, Centaur Warrunner, Bristleback, Medusa, Mars.

* Heroes with both illusions and summons, for Io has nothing to deal with multiple enemies at once outside from Spirits's weak area-of-effect: Beastmaster, Broodmother, Chaos Knight, Lycan, Naga Siren, Nature's Prophet, Phantom Lancer, Shadow Shaman, Terrorblade, Visage, Warlock, Wraith King.

* Heroes that are hard to gank: Axe, Death Prophet, Phantom Lancer, Slark, Centaur Warrunner, Bristleback, Medusa, Mars.

* Heroes with both illusions and summons, for Io has nothing to deal with multiple enemies at once outside from Spirits's weak area-of-effect: Beastmaster, Broodmother, Chaos Knight, Lycan, Naga Siren, Nature's Prophet, Phantom Lancer, Shadow Shaman, Terrorblade, Visage, Warlock, Wraith King.

* Heroes with both illusions and summons, for Io has nothing to deal with multiple enemies at once outside from Spirits's weak area-of-effect: Beastmaster, Broodmother, Chaos Knight, Lycan, Naga Siren, Nature's Prophet, Phantom Lancer, Shadow Shaman, Terrorblade, Visage, Warlock, Wraith King.

* Heroes that can easily bypass Io's allies to get to Io: Riki, Tusk, Clinkz, Sniper, Slark, Phantom Assassin, Void Spirit, Storm Spirit, Ember Spirit, Earth Spirit, Spirit Breaker, Lifestealer.

* Fragile heroes: Bounty Hunter has decent nuking capabilities with Shiruken Toss and Jinada thus making fragile heroes easy picks for ganking. Few examples of such heroes are:Crystal Maiden, Pugna, Skywrath Mage, Io, Witch Doctor, etc.

* Heroes that are hard to gank: Axe, Death Prophet, Phantom Lancer, Slark, Centaur Warrunner, Bristleback, Medusa, Mars.

* Heroes with either magical, physical or pure damage burst: Bane, Ember Spirit, Leshrac, Lina, Luna, Nyx Assassin, Phantom Assassin, Skywrath Mage, Tinker, Ursa, Void Spirit.

* Heroes that are hard to gank: Axe, Death Prophet, Phantom Lancer, Slark, Centaur Warrunner, Bristleback, Medusa, Mars.

* Heroes whose abilities can affect multiple enemies at once: Dawnbreaker, Ember Spirit, Lina, Luna, Jakiro, Leshrac, Invoker, Muerta, Dazzle.

* Heroes that can easily bypass Io's allies to get to Io: Riki, Tusk, Clinkz, Sniper, Slark, Phantom Assassin, Void Spirit, Storm Spirit, Ember Spirit, Earth Spirit, Spirit Breaker, Lifestealer.

* Heroes that can easily bypass Io's allies to get to Io: Riki, Tusk, Clinkz, Sniper, Slark, Phantom Assassin, Void Spirit, Storm Spirit, Ember Spirit, Earth Spirit, Spirit Breaker, Lifestealer.

* Queen of Pain can be a good hero for dealing with Ember Spirit with Orchid Malevolence, her pure damage nuke in Sonic Wave and a slow in Shadow Strike. However, Queen of Pain can be punished by Ember Spirit, as his Searing Chains prevents her from getting Blink off.

* Heroes that can easily bypass Io's allies to get to Io: Riki, Tusk, Clinkz, Sniper, Slark, Phantom Assassin, Void Spirit, Storm Spirit, Ember Spirit, Earth Spirit, Spirit Breaker, Lifestealer.

* Storm Spirit is not only a potent Orchid Malevolence carrier, his Electric Vortex provides an additional disable and Overload provides a great slow. When paired with Static Remnant, they can cut through Flame Guard fast.
* Ball Lightning not only provides great initiation upon Ember Spirit from any position anytime, but also helps dodge Sleight of Fist.

* Anti-mage is potentially good against Ember Spirit since he can burn Ember Spirit's mana, prevent him from escaping or using his skill. Anti-Mage has high magic resistance, which will reduce most of the damage from Ember Spirit's skill set. However, Anti-Mage lacks any form of stuns or lockdowns, and may struggle to kill Ember Spirit if he still has some mana left.

* Any Hero with high mobility will be neutralized by dream coil: Queen of Pain, Storm Spirit, Ember Spirit, Lycan, Bloodseeker, Anti-Mage, Timbersaw.

* Heroes that are hard to gank: Axe, Death Prophet, Phantom Lancer, Slark, Centaur Warrunner, Bristleback, Medusa, Mars.

* Heroes that can easily bypass Io's allies to get to Io: Riki, Tusk, Clinkz, Sniper, Slark, Phantom Assassin, Void Spirit, Storm Spirit, Ember Spirit, Earth Spirit, Spirit Breaker, Lifestealer.

* Disruptor can always Glimpse back Io or his target after he Relocated nearby.
* Even better, thanks to the indicator on the ground, you can even preemptively drop Static Storm and Kinetic Field on the spot they will relocate to.
* Thunder Strike and Glimpse are also good tools to bring back an Io that Tethered away in the fog of war.
Additional:
* Glimpse directly negates Relocate.
* Kinetic Field prevents Io from escaping with Tether.
* Static Storm can silence and damage both, Io and it's tethered target. And it can also mute both, Io and it's tethered target when upgraded with Aghanim's Scepter.

* Jakiro's area-of-effect ability arsenal allows him to affect multiple heroes at once, giving Io difficulties in saving them as he can only heal one hero at a time with Tether.
* Ice Path can be used to cancel both, Tether and Relocate.
* Jakiro commonly buys Rod of Atos that can be used to cancel Relocate, prevent Io in escaping with Tether and make Io easy target for Ice Path and Macropyre.
Additional:
* Jakiro's area-of-effect ability arsenal allows him to affect multiple heroes at once, giving Io difficulties in saving them as he can only heal one hero at a time with Tether.
* Ice Path can be used to cancel both, Tether and Relocate.
* Jakiro commonly buys Rod of Atos that can be used to cancel Relocate, prevent Io in escaping with Tether and make Io easy target for Ice Path and Macropyre.

* Homing Missile can be used to cancel escape attempts with Relocate.
* Flak Cannon allows Gyrocopter to attack both, Io and his Tethered target, especially when upgraded with Aghanim's Scepter.
* Rocket Barrage and Call Down allow Gyrocopter to deal serious damage to both Io and his Tethered target.
Additional:
* Homing Missile can be used to cancel escape attempts with Relocate.
* Flak Cannon allows Gyrocopter to attack both, Io and his Tethered target, especially when upgraded with Aghanim's Scepter.
* Rocket Barrage and Call Down allow Gyrocopter to deal serious damage to both Io and his Tethered target.

* Ensnare and Song of the Siren can be used to cancel both, Tether and Relocate and to close the distance on Io.
* Rip Tide combined with illusions from Mirror Image often finish off Io before he can save himself with Tether or Relocate.
* Spirits's weak area-of-effect makes it a bad tool to deal with Naga Siren's illusions from Mirror Image.
* Once Naga Siren buys Aghanim's Scepter, she can gain access to Reel In, which not only allows her to cancel both, Tether and Relocate, but also to pull Io to herself and her team while he is affected with Ensnare, similarly to Batrider's Flaming Lasso.
* Aghanim's Shard upgraded Song of the Siren can also heal the hero Io and his Tethered targed try to gank.
Additional:
* Ensnare and Song of the Siren can be used to cancel both, Tether and Relocate and to close the distance on Io.
* Rip Tide combined with illusions from Mirror Image often finish off Io before he can save himself.
* Spirit's weak area-of-effect makes it a bad tool to deal with Naga Siren's illusions from Mirror Image.
* Once Naga Siren buys Aghanim's Scepter, she can gain access to Reel In, which not only allows her to cancel both, Tether and Relocate, but also to pull Io to herself and her team while he is affected with Ensnare, similarly to Batrider's Flaming Lasso.
* Aghanim's Shard upgraded Song of the Siren can also heal the hero Io and his tethered targed try to gank.

* Heroes with both illusions and summons, for Io has nothing to deal with multiple enemies at once outside from Spirits's weak area-of-effect: Beastmaster, Broodmother, Chaos Knight, Lycan, Naga Siren, Nature's Prophet, Phantom Lancer, Shadow Shaman, Terrorblade, Visage, Warlock, Wraith King.

* 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

* Take Aim and Assassinate allow Sniper to reach Io even if it stays in the backline.

* Heroes with both illusions and summons, for Io has nothing to deal with multiple enemies at once outside from Spirits's weak area-of-effect: Beastmaster, Broodmother, Chaos Knight, Lycan, Naga Siren, Nature's Prophet, Phantom Lancer, Shadow Shaman, Terrorblade, Visage, Warlock, Wraith King.

* Heroes with either magical, physical or pure damage burst: Bane, Ember Spirit, Leshrac, Lina, Luna, Nyx Assassin, Phantom Assassin, Skywrath Mage, Tinker, Ursa, Void Spirit.

* Squishy heroes (Io, Crystal Maiden, Lina...), as Earth Spirit can deal tons of damage with Magnetize.

* Heroes with both illusions and summons, for Io has nothing to deal with multiple enemies at once outside from Spirits's weak area-of-effect: Beastmaster, Broodmother, Chaos Knight, Lycan, Naga Siren, Nature's Prophet, Phantom Lancer, Shadow Shaman, Terrorblade, Visage, Warlock, Wraith King.

* Heroes with either magical, physical or pure damage burst: Bane, Ember Spirit, Leshrac, Lina, Luna, Nyx Assassin, Phantom Assassin, Skywrath Mage, Tinker, Ursa, Void Spirit.

* Heroes with both illusions and summons, for Io has nothing to deal with multiple enemies at once outside from Spirits's weak area-of-effect: Beastmaster, Broodmother, Chaos Knight, Lycan, Naga Siren, Nature's Prophet, Phantom Lancer, Shadow Shaman, Terrorblade, Visage, Warlock, Wraith King.

* Terrorblade can easily take advantage of Io's weak durability with Reflection and Metamorphosis.
* As Io relies on boosting his and his Tethered target's attack speed with Overcharge, Terrorblade can take advantage of this with Reflection, which can damage and slow both, Io and his Tethered target.
* Spirits's weak area-of-effect makes it a bad tool to deal with Terrorblade's illusions from Conjure Image and Manta Style.
* Io's damage output is one of the weakest, therefore Terrorblade will have plenty of time to save himself with Sunder.
* However, Terrorblade has no way of stopping Io to escape with Tether or to stop both, Io and his Tethered target to escape with Relocate besides Terror Wave from Aghanim's Scepter.
Additional:
* Terrorblade can easily take advantage of Io's weak durability with Reflection and Metamorphosis.
* As Io relies on boosting his and his Tethered target's attack speed with Overcharge, Terrorblade can take advantage of this with Reflection, which can damage and slow both, Io and his Tethered target.
* Spirits's weak area-of-effect makes it a bad tool to deal with Terrorblade's illusions from Conjure Image and Manta Style.
* Io's damage output is one of the weakest, therefore Terrorblade will have plenty of time to save himself with Sunder.
* However, Terrorblade has no way of stopping Io to escape with Tether or to stop both, Io and it's Tethered target to escape with Relocate besides Terror Wave from Aghanim's Scepter.

* Heroes whose abilities can affect multiple enemies at once: Dawnbreaker, Ember Spirit, Lina, Luna, Jakiro, Leshrac, Invoker, Muerta, Dazzle.

* Heroes with both illusions and summons, for Io has nothing to deal with multiple enemies at once outside from Spirits's weak area-of-effect: Beastmaster, Broodmother, Chaos Knight, Lycan, Naga Siren, Nature's Prophet, Phantom Lancer, Shadow Shaman, Terrorblade, Visage, Warlock, Wraith King.

* Heroes with both illusions and summons, for Io has nothing to deal with multiple enemies at once outside from Spirits's weak area-of-effect: Beastmaster, Broodmother, Chaos Knight, Lycan, Naga Siren, Nature's Prophet, Phantom Lancer, Shadow Shaman, Terrorblade, Visage, Warlock, Wraith King.

* Charge of Darkness can be used to escape or counter-initiate against a Relocate gank.
* Greater Bash and Nether Strike is devastating due to Io's low armor, and can even knock it away from his Tethered target.

* Heroes with either magical, physical or pure damage burst: Bane, Ember Spirit, Leshrac, Lina, Luna, Nyx Assassin, Phantom Assassin, Skywrath Mage, Tinker, Ursa, Void Spirit.

* Thirst allows Bloodseeker to see where Io relocated to, should either Io or the tethered hero have low health.
* Rupture forces Io to stay in place, preventing it from using the Tether bonus movement speed to escape.

* Duel is very effective against Io due to its low health and armor.