Treant Protector
* 
Doppelganger can dispel Leech Seed. It can also destroy large amounts of trees, counteracting Nature's Guise and Eyes in the Forest.
Medusa
* Phantom Lancer with 
Diffusal Blade will very quickly burn Medusa's mana, making Mana Shield significantly less effective.
* Doppelganger's 1 second invulnerability can be used to dodge Medusa's petrification from Stone Gaze, as well as Mystic Snake.
* Phantom Lancer's illusions outnumber Medusa's targets from Split Shot, likely shielding his team in the process.
Treant Protector
* Heroes that depend on disrupting fights with ability combos or big ultimate abilities are vulnerable to the long stun of Fiend's Grip: 
Disruptor, 
Death Prophet, 
Enigma, 
Faceless Void, 
Invoker, 
Lich, 
Magnus, 
Mars, 
Medusa, 
Outworld Destroyer, 
Phoenix, 
Puck, 
Queen of Pain, 
Shadow Fiend, 
Treant Protector, 
Underlord, 
Winter Wyvern, 
Witch Doctor, 
Zeus.
Medusa
* Fiend's Grip provides mana drain, which can heavily damage 
Mana Shield and prevent Medusa from using 
Stone Gaze.
* Even if she does use Stone Gaze, Nightmare can buy enough time to protect allies and reset the fight.
Additional:
* 
Fiend's Grip leaves Medusa defenseless, since not only does it deal damage, it also drains mana.
Medusa
* He can use either his own or his double's 
Flux to bypass the spellblock from Linken's Sphere, using the leftover Flux + 
Spark Wraith to slow Medusa's already low move speed to a crawl.
* Arc Warden has a farming advantage with double 
Hand of Midas, and can generally bully Medusa with other items that benefit from duplication.
Medusa
* 
Vendetta burns a significant amount of mana on hit, and the damage from the ability drains Medusa's mana pool even further.
* Due to the passive nature of Mystic Snake and Split Shot, it can possibly proc Nyx's 
Spiked Carapace if he's within range of Medusa's abilities and isn't invisible.
* Medusa lacks single target damage, making Nyx with 
Aghanim's Scepter extremely hard to deal with if Medusa is the team's main damage source.
Additional:
* With her passive 
Split Shot, Medusa can be easily interrupted by Spiked Carapace during combat, especially during her precious Stone Gaze.
* Mana Burn quickly destroys Mana Shield, especially if Medusa only increases her mana pool by bolstering intelligence (which has the added bonus of increasing Mana Burn's damage).
* Uncontrollable damage from 
Mystic Snake and Split Shot can trigger Spiked Carapace.
* Medusa lacks single target damage, making a Burrowed Nyx Assassin hard to kill.
Medusa
* Ursa's status resistance from 
Enrage reduces duration of Medusa's Stone Gaze.
* Ursa can stack damage with 
Fury Swipes easily against her Mana Shield in a prolonged team match.
Additional:
* Medusa's tankiness doesn't help her very much against Fury Swipes in long teamfights.
* With no escape mechanism and a slow movement speed, getting jumped on by Ursa usually spells a quick end for Medusa in the early game.
Medusa
* Silencer burns easily through her effective HP from Mana Shield, by taking away her intelligence.
* 
Arcane Curse punishes her repeatedly casting Mystic Snake to keep her mana pool high. He can force her to use 
Manta Style before he has cast 
Global Silence and Medusa usually does not want to build 
Black King Bar.
Medusa
* 
Burning Spear's damage over time can rapidly burn Medusa's mana and health alike.
* 
Inner Fire can slow and disarm Medusa and also allow Huskar to follow up with Life Break.
Medusa
* With 
Smoke Screen, Riki will silence and catch Medusa in a surprise with high miss chance flushing her from positions easily in team fights.
* He can deal a huge amount of damage through 
Cloak and Dagger, even through Mana Shield.
Treant Protector
* 
Living Armor can be destroyed quickly with Ion Shell.
Medusa
* E.M.P. allows Invoker to burn Medusa's mana to weaken Mana Shield.
* Medusa's lack of mobility makes her easy to kite with Invoker's spells.
Additional:
* 
E.M.P. is a large mana burn nuke which can hit Medusa's Mana shield with enough damage to lose even more mana.
* 
Deafening Blast disarms Medusa's ability to deal pseudo-AOE damage during teamfights.
* 
Cold Snap allows the opposing team to repeatedly stun Medusa in short succession, preventing her from successfully casting her ultimate due to its long cast time.
Medusa
* Medusa lacks mobility or escape mechanisms. 
Earth Spike and 
Hex can neutralize her strong damage potential and allow for 
Lion's team to focus her down.
* 
Mana Drain is a perfect ability to weaken Medusa's durability as it can quickly drain her Mana Shield, making her far less tanky. Mana Drain can also be used to restore mana of Lion's allies, which can nullify the mana steal from Mystic Snake.
* Mana Drain, along with Hex, destroy illusions instantly, which may be extremely helpfull and efficient against core builders of Manta Style, like Medusa herself.
Treant Protector
* 
Corrosive Haze will reveal Treant Protector even when he is under the effects of Nature's Guise.
Medusa
* Other heroes who has armor and slow debuffs won't allow Medusa to disengage from combat: 
Tidehunter, 
Bristleback, 
Slardar.
Medusa
* Medusa cares less than other heroes about armor reduction, since Mana Shield blocks 70% of all damage without taking armor/magic resistance into consideration. This makes 60% of your Corrosive Haze ineffective until Medusa's mana is drained.
Treant Protector
* Timbersaw can use his plethora of tree cutting abilities to level entire sections of the forest, making hiding in the trees more difficult for Treant Protector and his team.
* Timbersaw can easily cut down Treant Protector's 
Eyes In The Forest once his team has detection. He may even do it unknowingly due to the sheer destructive and chaotic nature of his abilities.
Additional:
* Not only are all of Timbersaw's active abilities capable of cutting down trees, but 
Whirling Death and 
Timber Chain also require it to be effective, counteracting both Treant Protector's Nature's Guise and Eyes in the Forest abilities.
Treant Protector
* With Dual Breath, Liquid Fire and Macropyre Jakiro can quickly remove all Living Armor from a target.
* Ice Path allows Jakiro to prevent Treant Protector from using 
Overgrowth while staying at a safe distance.
Medusa
* With 
Static Link, Razor can effectively make Medusa useless in teamfights by reducing her main damage output. It can, however, be blocked by a 
Linken's Sphere.
* 
Plasma Field allows Razor to get on top of Medusa, slowing her already slow movement speed to a mere crawl.
* 
Eye of the Storm capitilizes on Medusa's low armor and causes her to be very vulnerable, even through Mana Shield.
Medusa
* Medusa is especially vulnerable to 
Essence Shift, as both strength and intelligence contribute to her effective HP, while agility contributes to her damage.
* 
Dark Pact when timed right can be used to dispel Stone Gaze right after it petrifies Slark, allowing him to keep attacking Medusa throughout the duration.
Additional:
* Medusa cannot chase Slark in any way and has no disable beyond her ultimate, making her unable to stop him getting away and regenerating before coming back to finish her off.
* Essence Shift particularly removes 1 intelligence point per hit, thus lowering Medusa's mana pool's cap and leaving her much more vulnerable in prolonged fights.
Treant Protector
* All of Treant Protector's abilities are worth stealing, and Rubick is able to cast them with no animation time.
Treant Protector
* Heroes with the capability of removing or destroying trees greatly hinders the effectiveness of Treant Protector's abilities: 
Batrider, 
Nature's Prophet, 
Lina, Enigma, Mars
Medusa
* 
Bulwark can make each of Medusa's attacks target him instead, reducing Medusa's contribution on team fights.
* 
Spear of Mars stuns Medusa and also pushes her away from teamfights, taking advantage of Medusa's low mobility.
* 
Arena Of Blood blocks Medusa's attacks from outside the arena.
Medusa
* Medusa's Stone Gaze forces Mars to choose between getting petrified, or turning his vulnerable back on Medusa.
Treant Protector
* Nature's Prophet's Nature's Call can destroy trees that Treant Protecter is hiding in, revealing him.
Treant Protector
* Firefly will cut trees with ease, cleaning-up an area that's been enchanted with Eyes In The Forest, and potentially revealing a Treant under the effects of 
Nature's Guise.
* Batrider's DoT spells are also good versus Living Armor.
Treant Protector
* Invisibility reliant heroes: Heroes with invisibility abilities or those that have invested into invisibility items are hindered by Bounty Hunter's Track. Few examples of such heroes are:
Clinkz, 
Riki, Treant Protector, etc.
Medusa
* Heroes who take a long time to become strong are in for a rough mid game, such as Outworld Destroyer, Magnus, Medusa, and 
Anti-Mage.
Treant Protector
* Melee heroes with low mobility can be kited and killed by Viper: Treant Protector, 
Kunkka, 
Alchemist, 
Troll Warlord, 
Wraith King, 
Tiny, 
Sven.
Medusa
* 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.
Medusa
* Heroes with extremely slow movement speed will cripple against Solar Bind: Medusa, 
Viper
Additional:
* 
Will-O-Wisp will keep Medusa busy after she got hit by 
Blinding Light.
Medusa
* Other heroes who has armor and slow debuffs won't allow Medusa to disengage from combat: Tidehunter, Bristleback, Slardar.
Medusa
* Hard carries who just want to farm and be left alone will not appreciate Primal Beast, heroes such as Medusa, 
Drow Ranger...
Medusa
* Other heroes who has armor and slow debuffs won't allow Medusa to disengage from combat: Tidehunter, Bristleback, Slardar.
Medusa
* 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.
Treant Protector
* Light Strike Array and Dragon Slave allows Lina to destroy trees, countering Nature's Guise and Eyes in the Forest.
* Lina has many tools to bypass Living Armor's protection.
Medusa
* Heroes with a lot of burst damage, especially those who rely on casting spells: Lina, Zeus.
Medusa
* Sniper can outrange both Medusa's arrows and Stone Gaze, allowing him to focus her down during a teamfight.
Additional:
* Medusa is a fairly immobile hero that deals damage around her with Split Shot. Sniper should outrange her and should stay out of harm's way from Split Shot.
* More importantly, Sniper should have enough attack range to fire at Medusa during her Stone Gaze without turning to stone, so the ultimate is mostly wasted against him.
Treant Protector
* Clinkz, 
Sniper, 
Lone Druid, Troll Warlord, 
Legion Commander and Wraith King are some of the Heroes that base themselves on attacks with little or no spell power, so they suffer in the grassy hands of Overgrowth.
Treant Protector
* Monkey King is one of the few other heroes who can easily traverse through trees, counteracting Treant Protector's ability to hide in trees.
Treant Protector
* Heroes that can maintain vision on Monkey King can see when he uses Tree Dance: 
Bloodseeker, Treant Protector with Eyes In The Forest, Sniper, 
Weaver
Treant Protector
* 
Nature's Grasp severely slows down Spirit Breaker, reducing effects of Charge of Darkness and Greater Bash.
* Living Armor can mitigate a large portion of Spirit Breaker's damage since his attacks are slow.
* Treant Protector can also counter-initiate against Spirit Breaker with 
Leech Seed, Overgrowth and with his root from 
Aghanim's Shard upgraded Nature's Guise before he manages to escape.
* Aghanim's Scepter gives Treant Protector access to Eyes In The Forest ability, which allows him to turn trees into wards that provide vision, allowing him to keep his allies warned about Spirit Breaker's attempts to gank them. Eyes In The Forest will also trigger Overgrowth if Spirit Breaker is in range of the tree affected by it.
Additional:
* Spirit Breaker's slow attacks cannot harm a hero shielded by Living Armor.
Medusa
* If Medusa activates Stone Gaze before Spirit Breaker reaches her with Charge of Darkness, the charge will inevitably fail.
* Medusa has three ways to counter Spirit Breaker's Charge of Darkness: Stone Gaze can disable Spirit Breaker's Charge of Darkness if he faces Medusa directly. Aghanim's Scepter upgraded Mystic Snake can disable Spirit Breaker and cancel his Charge of Darkness if it hits him. And 
Cold Blooded provided by Aghanim's Shard that can cast a single-targeted Mystic Snake at Spirit Breaker if he uses Charge of Darkness on her.
* Mana Shield and overall tankiness allows Medusa to easily survive Spirit Breaker's initiation. And to make things worse, Spirit Breaker is not a common Diffusal Blade nor 
Disperser wielder to counter this problem at all.
* Overall, any attempt for Spirit Breaker to gank and kill Medusa will hurt him more than the other way around.
Treant Protector
* Heroes with powerful rooting abilities will disable most of Pangolier's skills, a bonus point if it pierces 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
Medusa
* Split Shot will keep attacking Pangolier even when he is rolling around.
* Stone Gaze stuns Pangolier during Rolling Thunder, or forces him to roll away.
Treant Protector
* Overgrowth prevents Phantom Assassin from using 
Blink Strike even through her spell immunity.
* Living Armor reduces Phantom Assassin's physical damage whenever she attempts to gank an allied hero.
Medusa
* Heroes with disables that ignore spell immunity will render Phantom Assassin completely useless in teamfights throughout the game: 
Axe, Enigma, 
Vengeful Spirit, 
Doom, 
Bane, 
Beastmaster, 
Pudge, Medusa, 
Warlock.
Treant Protector
* Treant Protector can usually scout out Magnus in the trees with Eyes in the Forest and disrupt his initiation attempts. He can also counter Magnus' initiation with Overgrowth.
Medusa
* 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, Medusa, 
Dawnbreaker.
Treant Protector
* Treant Protector grants protection against his attacks with Living Armor and his ultimate, Overgrowth is a massive AoE disarm and root that pierces spell immunity, causing trouble to Lycan. You will find yourself in need of an ally's dispel or forced to pop Black King Bar for its dispel.
Additional:
* Lycan has no kind of teleport, being only able to walk, and heavily relies on his attacks. As Overgrowth roots and disarms the targets, Lycan can't do much in an overgrowth field.
Medusa
* Her Mana Shield is too tough for Lycan to break.
* Mystic Snake can hit for a massive damage once it spread between his summons.
Additional:
* Can be easily petrified despite his speed.
* Summoned wolves will be targeted by Split Shot or Mystic Snake
Treant Protector
* 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.
Medusa
* Heroes that are hard to gank: Axe, Death Prophet, 
Phantom Lancer, Slark, 
Centaur Warrunner, Bristleback, Medusa, Mars.
Treant Protector
* Heroes with global abilities can give Legion Commander's opponent an edge in Duels from anywhere on the map: Nature's Prophet, 
Ancient Apparition, Zeus, Invoker, Treant Protector
Medusa
* Mana Shield makes Medusa very hard to take down in Duels.
* Stone Gaze stops Legion Commander from Dueling altogether, regardless of who she targets.
Treant Protector
* Heroes that provide vision will see Fiend's Gate coming: 
Techies, 
Templar Assassin, Treant Protector.
Medusa
* Heroes with strong area-of-effect damaging and/or disabling abilities will be able to intercept Underlord and his team when they exit from Fiend's Gate: Luna's Aghanim's Scepter upgraded 
Eclipse, Dawnbreaker's 
Solar Guardian, Axe's 
Berserker's Call, Mars's Arena of Blood, Jakiro's 
Macropyre, 
Dual Breath and 
Ice Path, Naga Siren's 
Song of the Siren, Razor's Eye of the Storm and Plasma Field, Lina's 
Light Strike Array, 
Broodmother's 
Spinner's Snare from Aghanim's Scepter, Elder Titan's 
Earth Splitter and 
Echo Stomp, Alchemist's 
Unstable Concoction and 
Acid Spray, Queen of Pain's 
Sonic Wave, 
Dark Seer's 
Wall of Replica and 
Vacuum, Venomancer's 
Noxious Plague and 
Poison Nova from Aghanim's Scepter, Oracle's 
Fortune's End and 
Rain of Destiny from Aghanim's Shard, Bloodseeker's 
Blood Rite, Enigma's 
Black Hole and 
Midnight Pulse, Shadow Fiend's 
Requiem of Souls, Batrider's Aghanim's Scepter upgraded 
Flaming Lasso, 
Firefly, 
Flamebreak and 
Sticky Napalm, Ancient Apparition's 
Ice Blast, Sand King's 
Epicenter, 
Sand Storm and 
Burrowstrike, 
Gyrocopter's 
Call Down, 
Ember Spirit's 
Sleight of Fist, Death Prophet's 
Exorcism and 
Silence, 
Monkey King's 
Wukong's Command, Crystal Maiden's 
Freezing Field, 
Muerta's 
The Calling, Medusa's Stone Gaze, Zeus's 
Nimbus from Aghanim's Scepter. Dark Willow's 
Bramble Maze, 
Pangolier's 
Swashbuckle, 
Grimstroke's 
Soulbind, 
Ink Swell and 
Stroke of Fate, 
Earthshaker's 
Echo Slam and 
Fissure, Puck's 
Dream Coil and 
Waning Rift, Winter Wyvern's 
Winter's Curse, Magnus's 
Reverse Polarity.
Medusa
* Medusa's Split Shot can easily kill Chen's creeps.
* Mystic Snake can quickly kill Chen's creeps and deal intense damage for every killed creep while also draining their mana with each bounce. Aghanim's Scepter upgraded Mystic Snake can also disable both, Chen and his creeps upon impact.
* Mana Shield will make it impossible for Chen to burst down Medusa.
* Stone Gaze can disable Chen from using 
Hand of God to save himself or his allies.
Medusa
* Doom does not disable Mana Shield. As such, Doom's damage is largely mitigated by her mana shield. Additionally, Medusa is not reliant on her abilities to be effective during a teamfight, making Medusa an unproductive hero to target.
* Medusa is an ideal Linken's Sphere carrier. Should one be purchased, and without any additional disables, Doom may find that few opportunities exist to effectively lockdown, disable, and kill Medusa.
Medusa
* Enchantress often has a small army of neutral creeps, allowing Medusa to hit her with a later bounce of her Mystic Snake.
Treant Protector
* Treant can give chase should Hoodwink attempt to 
Scurry away, and Nature's Grasp can slow her down so Treant Protector's teammates can pin Hoodwink down.
Medusa
* Stone Gaze allows Medusa to easily kite and kill Sven.
* Mana Shield negates much of Sven's burst damage.
Additional:
* Mana Shield makes it very hard for Sven to burst her within Storm Hammer's stun duration.
* Stone Gaze makes it very difficult for Sven to fight Medusa at any stage of the game.
* Mystic Snake can slow Sven down enough for allies to capitalize on his commitment in a fight.
Treant Protector
* If 
Storm Spirit is caught in an Overgrowth, he is shut down.
* With the exception of 
Electric Vortex, he won't be able to cast any relevant skill.
Medusa
* Mana Shield can tank most of the damage from Reaper's Scythe; with sufficient mana, the kill threshold drops significantly.
* Necrophos has a movement speed equal to Medusa, and is easy to chase down with a slowing item in Medusa's inventory.
Treant Protector
* Another hero heavily based on attacks and no mobility, being an easy prey for Treant strong disarms and motion reduction skills.
Treant Protector
* Clinkz will often roam the map alone, and Treant Protector's Nature's Guise allows him to set up kills with his allies on Clinkz from invisibility.
* Treant Protector's very high damage allowing him to trade hits or contest last hits with Clinkz, while Living Armor can be used to sustain the harass.
* Living Armor protects any of Treant's allies ganked by Clinkz.
* In teamfights, Treant Protector's Overgrowth can disarm Clinkz, preventing him from turning invisible and holding him in place even if he has a Black King Bar.
* Leech Seed slows Clinkz, preventing him from repositioning or fleeing away from danger.
Medusa
* Poof won't damage Medusa and she can use Stone Gaze to disable all of Meepo's clones.
* Mystic Snake will easily become the bane of Meepo early game.
Medusa
* Split Shot can destroy Tombstone Zombies and Tombstone itself while still damaging heroes.
Medusa
* Should Luna choose to buy Manta Style, Medusa will be able to kill illusions from them with Split Shot and 
Mjollnir, which is a common item on Medusa.
* Mystic Snake allows Medusa to easily harass Luna and steal mana from her, preventing Luna from retaliating with 
Lucent Beam.
* Medusa can survive Eclipse thanks to Mana Shield, which can cause Luna to struggle greatly in bursting down Medusa and force her to buy Diffusal Blade and it's upgrade Disperser.
* Even with Black King Bar, Medusa's Stone Gaze will still be able to disable Luna, which could even discourage her from counter-initiating with Eclipse.
Additional:
* Should Luna choose to buy Manta Style, Medusa will be able to kill illusions from them with Split Shot and Mjollnir, which is a common item on Medusa.
* Mystic Snake allows Medusa to easily harass Luna and steal mana from her, preventing Luna from retaliating with Lucent Beam.
* Medusa can survive Eclipse thanks to Mana Shield, and since Luna is not a hero that often goes for Diffusal Blade, she will struggle greatly in bursting down Medusa.
* Even with Black King Bar, Medusa's Stone Gaze will still be able to disable Luna, which could even discourage her from counter-initiating with Eclipse.
* For the same reasons, Medusa makes a very powerful ally for Luna when they are in the same team.
Medusa
* Visage's familiars are easy targets to Split Shot.
* Mana Shield will resist Soul Assumption instances without effort.
Medusa
* Lifestealer's low mobility makes him easy to kite.
* Stone Gaze pierces 
Rage, wasting its cooldown and making Lifestealer unable to fight.
Treant Protector
* Overgrowth has a great duration, which prevents the units caught from attacking, moving and Blinking. Heroes like Storm Spirit, 
Mirana, Anti-Mage and others won't be able to do much if they're caught.
Medusa
* Any long duration disables that can pierce through both, Pierce The Veil and Black King Bar are devastating against Muerta: Enigma's Black Hole, Dawnbreaker's Solar Guardian, Axe's Berserker's Call, Naga Siren's Aghanim's Scepter upgraded 
Ensnare and 
Reel In from Aghanim's Scepter, Jakiro's Aghanim's Scepter upgraded Macropyre, Bane's Fiend's Grip, Pudge's 
Dismember, Batrider's Flaming Lasso, Beastmaster's 
Primal Roar, Grimstroke's Soulbind, Medusa's Stone Gaze, Magnus's Reverse Polarity.
Medusa
* Heroes with Linken's Sphere as core item: Weaver, 
Morphling, Medusa.
Treant Protector
* Clinkz, Sniper, Lone Druid, Troll Warlord, Legion Commander and Wraith King are some of the Heroes that base themselves on attacks with little or no spell power, so they suffer in the grassy hands of Overgrowth.
Treant Protector
* Clinkz, Sniper, Lone Druid, Troll Warlord, Legion Commander and Wraith King are some of the Heroes that base themselves on attacks with little or no spell power, so they suffer in the grassy hands of Overgrowth.
Medusa
* Heroes with a lot of burst damage, especially those who rely on casting spells: Lina, Zeus.
Treant Protector
* Clinkz, Sniper, Lone Druid, Troll Warlord, Legion Commander and Wraith King are some of the Heroes that base themselves on attacks with little or no spell power, so they suffer in the grassy hands of Overgrowth.
Treant Protector
* Treant Protector's Living Armor will also negate Tidebringer's damage.
Medusa
* 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.
Medusa
* Medusa's Split Shot and Mystic Snake combined with Mjollnir, a common item for Medusa, will whittle down all of Naga Siren's illusions, including Naga Siren herself.
* Medusa's Stone Gaze can disable Naga Siren even for the duration of Song of the Siren and even if Naga Siren is spell immune, discouraging Naga Siren from even trying to use Song of the Siren to save herself or counter-initiate against Medusa.
Additional:
* Medusa's Split Shot and Mystic Snake combined with Mjollnir, a common item for Medusa, will whittle down all of Naga Siren's illusions, including Naga Siren herself.
* Medusa's Stone Gaze can disable Naga Siren even for the duration of Song of the Siren and even if Naga Siren is spell immune, discouraging Naga Siren from even trying to use Song of the Siren to save herself or counter-initiate against Medusa.
Treant Protector
* Heroes with the capability of removing or destroying trees greatly hinders the effectiveness of Treant Protector's abilities: Batrider, Nature's Prophet, Lina, Enigma, Mars
Medusa
* Medusa's Split Shot can make quick work of Enigma's Eidolons and take advantage of their considerable bounty.
* Medusa can also kill Eidolons with her Mystic Snake that can also greatly damage Enigma and drain some of his mana.
* If Medusa activates Stone Gaze at the start of a fight, it can make initiating and landing an effective Black Hole exceedingly difficult, because Stone Gaze can cancel Enigma's Black Hole even through spell immunity, which can discourage Enigma from even trying to initiate with Black Hole.
Additional:
* Medusa's Split Shot can make quick work of Enigma's Eidolons and take advantage of their considerable bounty.
* If Medusa activates Stone Gaze at the start of a fight, it can make initiating — and landing an effective Black Hole exceedingly difficult. Stone Gaze can cancel Enigma's Black Hole even through spell immunity, which can discourage Enigma from initiating with Black Hole.
Treant Protector
* Heroes with invisibility will be detected by Thirst when they have low enough health: 
Bounty Hunter, Templar Assassin, Riki, Clinkz, Weaver, Treant Protector, 
Nyx Assassin.
Medusa
* Mana Shield makes it very difficult for Bloodseeker to gain his Thirst bonuses.
* Rupture rarely kills Medusa through Mana Shield.
Medusa
* Anti-Mage easily destroys Mana Shield with Mana Break, especially once he has Manta Style.
* Anti-Mage effectively avoids Stone Gaze with Blink, and can reinitiate after its duration is over.
Additional:
* 
Mana Break burns Medusa's mana easily, especially when coupled with a Manta Style.
* Can easily initiate on Medusa with 
Blink, burning her mana or forcing her to use Stone Gaze.
* 
Mana Void is effective against Medusa's big mana pool and mana usage, presenting a huge hazard to Medusa's allies around her since her Mana Shield still gives her some protection if she has mana.
Treant Protector
* Anti-Mage relies on blinking and attacking. Overgrowth prevents both.
* Be wary that he will eventually farm up a Manta Style that fully dispels Overgrowth. Good players will wait for your ultimate to use their manta. Perhaps an ally has a silence or similar that would force him to use his manta before your ultimate.
Medusa
* Axe can take advantage of Medusa's awfully low HP to insta-kill her with 
Culling Blade, making it extremely difficult for her to farm for items to compensate for the lack of strength during early and mid-game while Axe is continuously harassing around.
Medusa
* Mana Shield reduces the effectiveness of Counter Helix.
* Stone Gaze makes it very difficult for Axe to initiate on Medusa and her allies.
Medusa
* 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.
Treant Protector
* 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.
Treant Protector
* Spiderlings melt away
Living Armor almost instantly.
Eyes In The Forest may prove dangerous for Broodmother, however.
* The vision from
Medusa
* Webbed areas can be used to hit and run, covering distance hastily weakening her on the way and initiating ganks.
Silken Bola will cause her attacks to miss and get her swarmed in no time.
Mana Shield fully while Broodmother can fit a 
Diffusal Blade to burn away all of Medusa's mana.
Spin Web will allow Broodmother to pick her own fights and sometimes slip away to ambush Medusa.
* Even though Medusa can hunt down Spiderlings easily when given enough range,
* Medusa usually does not build a Black King Bar to benefit from
Additional:
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* Though Medusa's Split Shot and Mystic Snake can help Medusa deal with Broodmother's spiderlings, Broodmother will create too much of them for her to handle, allowing her to outnumber Medusa's targets from Split Shot and shield her team in process.