Crimson Rock Hydra

With its body covered in lumpy reddish-grey scales that look like rock, the crimson rock hydra is an ambush hunter in the desert.
The hydra's five heads particularly resemble angular boulders, and it uses this to its advantage. Digging a shallow pit in the sand, it partially buries itself. With only its heads exposed and resembling a shady rock outcrop, it waits in torpor. When prey approaches, it wakes and strikes rapidly, its venom swiftly immobilising the prey animal.
The heads appear to be a pile of rocks on top of one another, and the long, serpentine necks are coiled beneath them to allow the hydra to strike rapidly in any direction. Usually one of the heads remains more wakeful than the rest, making it particularly difficult to surprise. Each head is able to make its own biting attack, and it is not uncommon for its prey to be rent apart in an explosion of gore as multiple savage strikes tear at it. When this happens, the hydra will relocate before laying its ambush again, to prevent the scent of blood from warning future prey.
When one of a rock hydra's heads is cut off, it regrows two more from the stump within moments. Only cauterising the wounds is sufficient to prevent this regrowth. As the heads regrow, it gains vitality in its maddened fury. Its lumpy scales also afford it a significant amount of protection, giving it natural armour. The necks are between ten and fifteen feet long, giving it an unexpected range as it strikes. An old hydra may have many more than five heads, with the necks protected by scaly rings of scar tissue, and is usually particularly vicious. Older hydras range far afield to satisfy their urge to hunt.