The Lernaean Hydra is the most common representant of the hydra dragon clade.It is mostly notable for its four heads and its poison breathe which can kill instantly any creature in one single blow,it is so poisonous even their tracks are deadly.A hydra is an especially deadly monster, since every time a head is severed; two new ones grow in its place. A hydra is not very intelligent, and therefore usually neutral in alignment. They usually live alone in swamps, marshes, and subterranean lairs and are generally the most dangerous predator in the area they inhabit.A hydra can be killed either by severing all its heads or by slaying its body. To prevent a severed head from growing back into two heads, at least 5 points of fire or acid damage must be dealt to the stump (a touch attack to hit) before the new heads appear. A flaming weapon (or similar effect) deals its energy damage to the stump in the same blow in which a head is severed. Fire or acid damage from an area effect may burn multiple stumps in addition to dealing damage to the hydra’s body. A hydra does not die from losing its heads until all its heads have been cut off and the stumps seared by fire or acid. Heracles used this trick to successfully defeat the original Hydra of Lerna.