In the Harry Potter series, there is a scene in which Luna Lovegood tells Harry that she, too, can see the horse-like creatures that pull the Hogwarts carriage. The thestrals, which are invisible to most of the other students, can only be seen by those who have witnessed, and accepted, death. Harry, who in the earlier books thought the coach flew on its own, had watched powerlessly as Voldemort killed Cedric. Once he has accepted that death, he sees the beasts for the first time.
They are described as horses with wings. But they bear no resemblance to the creatures we see on tee shirts and the covers of notebooks marketed to young girls, horses which tend to resemble Arabians, with their refined features, flowing manes and tails, and lovely floating action.
Nothing can prettify a thestral. Dark-colored and skeletal, with the naked leathery wings of a bat, it is fanged and carnivorous. Unless it is running free, it must be fed, and to do that, you have to go deep into the woods, their preferred habitat. Of course, the woods are not safe, and neither is the thestral. But, though never docile, it is useful and clever, with an unerring sense of direction. This last quality is particularly helpful, because we must often walk where the path is not marked, and wrong turnings are all too easy to make. It's also vexing, because we're human, and we often can't hear where our wise souls want to go. I think this combination of helpful and vexing is an attribute of the divine, and so I have a great respect for thestrals, and for J. K. Rowling for capturing them in words. I am fascinated by her vision of a direction-finder that can serve anyone, but is only visible to those who have witnessed and accepted death.
All creatures great and small, living and mythological (not always a contradiction) embody some aspects of the divine. Everything bears the fingerprints of God. Though the appearance of these beasts seems frightening, one must look again. After all, who is it in scripture whose appearance is so terrifying that the first words heard are always "fear not!"? Hint: it's not Satan.