Gesturing back to the space, Hermione asked Briallen what that was all about. Bri replied, "The carriages are pulled by a creature known as a Thestral. The best way to think of a Thestral is to view it as an inverse Pegasus. Instead of being a pale white well-fed horse with feathery wings, a Thestral looks like it was born to a bat that mated with a corpse of a horse. Wizards being who they are have labeled them as Dark creatures, but the ones here at the castle are nothing of the sort."