Dreambeast

Dreambeasts were strange creations made through the dark side of the Force. The appearance of such beasts was never the same, as they took on the shape of what the opponent feared most in their mind. This allowed it to take on a wide variety of appearances. When the creatures were killed, the physical wounds they left on their opponent would seem to disappear, suggesting that the creatures inflict a form of telepathic pain that borders on the real and the imaginary. Furthermore, the mental trauma inflicted by these creatures was permanent, and would render most victims mentally unstable in the future.

Text and facts from the “Dreambeast” article on Wookieepedia, licensed under CC BY-SA 3.0. Modified for this site.