Leviathan

The Leviathan, colloquially known as the Old One, is a colossal whale-like beast that lives near the Moonshae Isles. It was summmoned to existence by the Earthmother, goddess of the isles, and is considered one of her three "children" along with Kamerynn and the Pack. A passive, peaceful creature, the Leviathan is nonetheless catastrophically dangerous when provoked, sporting sharp teeth and a 360-foot length. It spends years sleeping at the bottom of the sea, emerging periodically to feed on small sea life. It is essentially on constant standby, ready to be called upon by the Earthmother when needed to preserve the balance of the isles. Like the other children of the Earthmother, the Leviathan is quasi-immortal: within a century of its death, another whale will assume its place as the Earthmother's chosen, but it will take many centuries for it to grow and develop into another Leviathan.