Nidmaw the Whalebird
The beast known as Nidmaw the Whalebird is (hopefully) the only one of its kind. A terrifying leviathan-creature, it is the Roc of the ocean – its beak strong enough to pierce hulls or snap masts, its massive body capable of toppling ships or flooding villages as it splashes across the waves.
Nidmaw is greedy; it seeks out wealthy ships and smashes them, swallowing their riches into its craw. Thus laden with treasure, it withdraws to strange waters, eluding capture or vengeance. Yet it also feeds on men and women, and on the seals which are its favored prey, especially the leopard seals that prey on smaller fowl.
Little is known about Nidmaw’s origin. It (or perhaps, its kind) seems to have come into Creation sometime after the Fair Folk invasion, perhaps hatched from a mutant egg, perhaps some beast of war abandoned by the Balorian princes. For years or decades it destroys, smashing ships, tearing down navies, only to withdraw again for decades on end into… where? The deeps? The West? Nobody knows.