Hydra ( enemy ) Hydra is a recurring enemy in the " Final Fantasy " series who first appeared in the first Final Fantasy game . They are usually a dragon or snake like creature with multiple heads . They commonly appear in rivers or lakes . Appearances . " Final Fantasy " . It first appears in the original " Final Fantasy " . It commonly appear in rivers around the world . " Final Fantasy III " . Found in World of Darkness as a rare enemy and palette - swap of Echidna . " Final Fantasy IV " . Hydra appears as a two headed snake found in the Ancient Waterway . " " . It appears the same like in original " Final Fantasy IV " , but in Ceodore ' s Tale . It also appears in Yang ' s Tale in the Adamant Forest and in Palom ' s Tale in Troia Waterway , Lodestone Cavern , and his Challenge Dungeon . " Final Fantasy V " . First time appearing as a dragon like enemy , the Hydra is found in the Ronka Ruins . " Final Fantasy XI " . Hydras are an uncommon type of Notorious Monster of the Dragon family . Hydras are unique in that dealing a Critical Hit may sever one of its three heads , denying it access to certain abilities . Only the left and right heads may be lost in this fashion . The left and right heads are responsible for Polar Bulwark , Pyrrhic Bulwark , Polar Blast , Pyrrhic Blast , and Nerve Gas Tactical Points abilities , and when the heads are removed , the monster ' s Regen and Regain traits disappear . With but one head , the creature only has recourse to Trembling , Serpentine Tail , and Barofield . Besides these abilities , hydras are immune to spiritual - type damage such as is inflicted by a Monk ' s Chi Blast or the Spirits Within weaponskill . They also enter a " rage mode " upon dropping below 25 % HP where their attack power increases , although this increase remains if their regen takes them above 25 % HP . Known NMs of the hydra type are : Pandemonium Warden also assumes a hydra form during the battle . Besides being a monster name , Hydra was also the name of the Server used for the beta test of the XBox 360 version of " Final Fantasy XI " . " Final Fantasy XIV " . The Hydra is a boss encountered in the trial " A Relic Reborn : The Hydra " as part of the Relic Weapon quest . Crucially , players must fight the Hydra with their unfinished relic weapons in order to complete the quest , putting themselves at a significant disadvantage as they are much weaker at that stage than other weapons of similar level . " Final Fantasy Tactics " . Hydras and their relatives , Greater Hydras and Tiamats , are arguably the strongest Monster units in the game . They can fly and use Tri - Attacks such as Tri - Thunder , dealing hundreds of damage to three random tiles in the attack radius . Physical attacks will never miss them because they have 0 Evasion . " Final Fantasy Mystic Quest " . The Dualhead Hydra , simply Hydra in the Japanese version , is one of the Vile Four , encountered in the Lava Dome . It is later reincarnated as the Twinhead Wyvern . " Final Fantasy Adventure " . The Hydra is a boss found within the Cave of Marsh . It shoots fireballs for its attack , and will drop the Mirror when defeated . " The Final Fantasy Legend " . The Hydra is an enemy and also a possible monster that the party ' s monster unit ( s ) can transform into . It can be found on the sixteenth floor of the Tower . " Final Fantasy Legend II " . The Hydra is an enemy and also a possible monster that the party ' s monster unit ( s ) can transform into . " Final Fantasy Legend III " . The Hydra is an enemy and also a possible monster that the party can transform into . " Final Fantasy Dimensions " . Hydra is an enemy family in " Final Fantasy Dimensions " . Members are winged dragons with five heads and two feet .