Valazio

The valazio is a large, swan-sized ultramarine magical bird with dark blue and black plumage, along with a black beak and talons, yellow eyes, and a tail as long as a peacock's. Its ultramarine feathers have a faint icy glow in darkness, while its black tail feathers are cool to the touch.

Valazios will usually nest near lakes and are fierce hunters, preferring to catch fish or other aquatic creatures. As valazios approach their Steaming Day, they resemble a half-plucked goose. Their eyes become dull, their feathers start to fall out, and they make choking noises. Then the bird suddenly bursts into steam only to rise from the puddle shortly after. In a number of days, they grow back to full size. Thanks to this ability, valazios live to an immense age, perhaps even forever.

It is a possible, rare corporeal form of the Patronus Charm