* 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:
* His Fiend's Grip will leave Medusa defenseless after he's done, if his teammates can provide cover for him or he initiates at the right time by Spell immunity.

* 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.

* 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.
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 and his Shadowraze.

* Nether Ward will cause an unfriendly area for Medusa, draining her mana.

* 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.
Additional:
* Sniper can outrange both Medusa's arrows and Stone Gaze, allowing him to focus her down during a teamfight.

* Shrapnel can be used to cancel Shadow Fiend's Blink Dagger from a huge range.
* Take Aim and Headshot allow Sniper to harass Shadow Fiend in lane without getting into the range of his Shadowraze.
* Assassinate can be used to cancel Shadow Fiend's Requiem of Souls if he is not a target.
Additional:
* Shrapnel can be used to cancel Shadow Fiend's Blink Dagger from a huge range.
* Take Aim and Headshot allow Sniper to harass Shadow Fiend in lane without getting into the range of his Shadowrazes.

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

* 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.
Additional:
* Level 4 Mana Burn burns 38,5% of Medusa's mana every 4 seconds if Medusa only increases her mana pool with intelligence. Additionally, 60% of the Mana Burn damage gets mitigated by Mana Shield, burning even more mana.
* 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.

* Heroes without escape mechanism: Shadow Fiend, Alchemist

Additional:
* 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.

* 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.
Additional:
* Ursa's status resistance from Enrage will ignore Medusa's gaze.
* Ursa can stack damage with Fury Swipes easily against her Mana Shield in a prolonged team match.

* Other heroes who has armor and slow debuffs won't allow Medusa to disengage from combat: Tidehunter, Bristleback, Slardar.

* 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.

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

* EMP 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.
Additional:
* EMP 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.

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

* 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.
* In addition to easily breaking her commonly bought Linken's Sphere with its low cooldown, Mana Drain can quickly drain her Mana Shield, making her far less tanky.

* 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:
* Anti-Mage's 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.

* 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

* He won't be around waiting for Medusa to Stone Gaze and pin him until she bears a true sight.
* 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 still deal huge amount of damage through Cloak and Dagger via backstabs, drying out Medusa's protection in a whim at random occassions.

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

* 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 skills in order to escape.
* If Shadow Fiend chooses to go for a right-click build, he'll have a hard time against Terrorblade's high armor.

* 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.

* Other heroes with mana burning or manipulating abilities will make Medusa much less tanky: Lion, Mirana, Weaver.

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

* 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.

* 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.

* 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.
Additional:
* 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.

* Unlike other illusion heroes, Tempest Double won't be instantly destroyed by Stone Gaze since it is considered a clone and not an illusion.
* 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 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.

* Void can be used to cancel Requiem of Souls.
* Crippling Fear prevents Shadow Fiend from using Shadowraze or Requiem of Souls.
* With Dark Ascension and Gem of True Sight, Night Stalker can find and kill Shadow Fiend easily. He is also a tanky hero that can fight Shadow Fiend at any stage of the game.

* 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 your team in the process.

* Lucent Beam and Eclipse with ministun talent can be used to cancel Requiem of Souls if Shadow Fiend does not have Black King Bar.
* Moon Glaives and Lunar Blessing allow Luna to outfarm Shadow Fiend in lane.
* A well timed Eclipse will burst and kill Shadow Fiend before he even 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.
* 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.

* Shadow Fiend's fragility and lack of a natural escape mechanism makes him a great target for Templar Assassin's Meld.
* Shadow Fiend's burst damage, such as Shadowraze and Requiem of Souls, is easily nullified by her Refraction.

* 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.

* Lacking escaping mechanisms, being dependent on fair positioning and channeling for his ultimate, its easier to Warlock with your long range crowd control abilities to lock the Shadow Fiend down to your team.

* 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.

* Other heroes who has armor and slow debuffs won't allow Medusa to disengage from combat: Tidehunter, Bristleback, Slardar.

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

* 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.

* Nethertoxin breaks both Necromastery and Presence of the Dark Lord, reducing his damage massively.
* Corrosive Skin gives Viper bonus Magic Resistance against Shadowraze and Requiem of Souls.
* Viper can easily take advantage of Shadow Fiend's lack of escape and mobility spells with Viper Strike and Poison Attack. Poison Attack also serves as a great way to harass Shadow Fiend.

* 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.

* Chakra Magic can drain her current mana, draining away her effective health in a sneaky way.
* Will-O-Wisp will keep Medusa busy after she got hit by Blinding Light.

* 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.

* 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.

* Heroes with channeling spells because Shadow Fiend has nothing to cancel channeling: Bane, Enigma, Pudge, Shadow Shaman.

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

* Other heroes with mana burning or manipulating abilities will make Medusa much less tanky: Lion, Mirana, Weaver.

* 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.

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

* Squishy heroes or heroes without hard disables or silences: Shadow Demon, Shadow Fiend, Venomancer, Ancient Apparition etc.

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

* 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 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.

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

* Heroes with channeling spells because Shadow Fiend has nothing to cancel channeling: Bane, Enigma, Pudge, Shadow Shaman.

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

* Other heroes who has armor and slow debuffs won't allow Medusa to disengage from combat: Tidehunter, Bristleback, Slardar.

* 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.

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

* 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.