The griffin, (or griffon, or gryphon) is, according to the lore, is a legendary creature with the body, tail, and back legs of a lion; the head and wings of an eagle; and an eagle's talons as its front feet. Because the lion was traditionally considered the king of the beasts and the eagle the king of birds, the griffin was thought to be an especially powerful and majestic creature.
Not much known about this creature. To date, Sam and Dean have never encountered an actual griffin. However, there are some clues that this creature exists. Gadreel stated that its feathers, along with bones of a fairy, is one of the ingredients needed to perform the Horn of Gabriel Sigil, that will lure any Angels to the sigil. Ian, the hunter, also had its feathers, and sold them secretly in his herbal remedies store.
It's unknown if the creature is closely related to the celestial beings like Angels.