Probably related to the Erycis, the Hydra does not, as the name suggests, regrow chopped off heads.
Regular reduce hero movement speed by 20%. Elite reduces hero speed by 30%.
Type: Anti Hero
Target Priority: Hero carrying crystal > Melee Hero = Lure Minor Module = Long Range Hero > Not Recruited Hero > (Elite: NPCs) > Crystal
Mob ID: Mob_C_Debuffer / Mob_C_Debuffer_Elite
Note: Hydras reduce the speed of heroes in the same room. This is in addition to the normal speed reduction due to having mobs in the room and not affected by Scamper.