* 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.

* Juxtapose and Doppelganger conjures too many illusions for Dazzle to deal with, given he has no inherent movement- or AoE-abilities.
* Phantom Rush and Spirit Lance allow Phantom Lancer to trivially catch Dazzle even in the back line of a fight.
* Phantom Lancer has high base armor which counters Dazzle's physcial damage based spells in lane.

* A well-timed Global Silence prevents Dazzle from saving allies with Shallow Grave or Shadow Wave. Items that could dispel the silence are expensive, and difficult for Dazzle to farm from a support role.
* Arcane Curse and Last Word cause long damage over time, which may outlast Shallow Grave.

* 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.

* Heroes with high burst damage through their physical attacks or spells can kill Dazzle or his allies before he has a chance to use Shallow Grave. (Lina, Lion, etc.)

* 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.

* Support heroes with low mobility can be slowed further by Incapacitating Bite, and swarmed by Spiderlings for an easy kill: Shadow Shaman, Visage, Dazzle, Rubick, Lich.

* Webbed areas can be used to hit and run, covering distance hastily weakening her on the way and initiating ganks.
* Even though Medusa can hunt down Spiderlings easily when given enough range, after an Incapacitating Bite she will get her swarmed in no time.
* Medusa usual do not build a BKB to benefit from Mana Shield fully while Broodmother can fit a Diffusal Blade to burn away mana.
Additional:
* Spin Web will allow Broodmother to pick her own fights and sometimes slip away to ambush Medusa.

* 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 in 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.

* 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.

* Some heroes with extreme range, like Zeus, Invoker or Clockwerk, can snipe your allies from anywhere after your Grave has expired.

* 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.
Additional:
* 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.

* Ice Blast negates healing from Shadow Wave, and lasts longer than Shallow Grave.
Additional:
* Shallow Grave prevents Ice Blast's shatter for up to 5 seconds, but can mostly only delay it as Ice Blast's debuff lasts 10 seconds and prevents Shadow Wave from healing them.

* Will-O-Wisp will keep Medusa busy after she got hit by Blinding Light.

* 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 at a whim.

* Nether Ward causes an unfriendly area for Medusa that drains her mana.

* 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.

* Astral Imprisonment is a versatile nuisance:
* If it is cast on a low-enough-health unit at least 1 second into Shallow Grave's duration, the Shallow Grave will end during the imprisonment, and the target will take lethal damage when released.
* It can be used remove Dazzle from the fight at a time he could have saved someone.
* It lets himself or an ally dodge all of Poison Touch's effects, for long enough to recover their Blink Dagger.

* 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, 70% 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.

* Because of her need to get status items early to tank it up, Rubick can greatly reduce her damage early with Fade Bolt
* Her stationary nature and the slow cast time of her spells makes it easier for Rubick to steal Stone Gaze or Mystic Snake
* Aghanim's Scepter's Mystic Snake is often better used by Rubick than by Medusa

* Laguna Blade can kill Dazzle quickly before he casts Shallow Grave.

* 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.

* 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, if Bane's teammates can cover him or he initiates at the right time by Spell immunity.

* 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 ignores Medusa's gaze.
* Ursa can stack damage with Fury Swipes easily against her Mana Shield in a prolonged team match.

* 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.

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

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

* 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.

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

* 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.

* Some heroes with extreme range, like Zeus, Invoker or Clockwerk, can snipe your allies from anywhere after your Grave has expired.

* Dazzle's lack of a true disable makes him a relatively vulnerable target for Phantom Assassin.
* Coup de Grace will often kill Dazzle's teammates before he has a chance to use Shallow Grave.

* 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 removes 1 of every attribute, lowering Medusa's mana pool's cap and leaving her much more vulnerable in prolonged fights.
Additional:
* 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.

* 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.

* Spectre's entire ability set is designed to get to and destroy heroes that stay in the backlines, both carries (like the aforementioned Drow Ranger and Sniper) and supports (like Dazzle and Shadow Shaman).