There is a flock of flightless birds that march through all space and time like little soldiers. Their beaks are butter, their skin pancakes, their innards made of well-done hamburger, lettuce, and cheese. Only their talons, sharp and long, are consistent with the meaning of the term "bird." They are not restricted to this form; their bodies can manifest as any manner of food, but their talons always remain the same. They walk on nothingness and through all things, forever moving in a single direction, going nowhere in particular. They are called the Pirajin.
Other beings constantly seek out the Pirajin to eat them. The Pirajin succumb easily; they do not flee. Until they are fell by the stomachs of greater beasts, they march on, undeterred by all manner of threats. Only by stating the true name of the Pirajin can one distract them from their eternal stroll of chaos.
When summoned, a Pirajin detracts its talons and is indistinguishable from ordinary food. Although they are delicious, a secret known only among the Pirajin is that he who is unfortunate enough to eat one will slowly transform into a new flock of them, consisting chiefly of his own meat. This is indirectly how all Pirajin came to be -- one existed at first, and it was eaten.