In the wake of the Jedi Civil War, storm beasts were the only visible beings that lived on the surface of Malachor V, aside from the inhabitants of the Trayus Academy.
Originally, they were natural creatures at the top of the food chain, until the Trayus Academy was constructed. The Sith used the dark side to turn the creatures into menacing beasts, who continued to be immersed in it well after the Sith left the planet. Following the second activation of the Mass Shadow Generator, which devastated the planet even further than it already was, many storm beasts died, although some lived on, able to sustainably live in what remained of Malachor's atmosphere..
- Star Wars: Knights of the Old Republic II: The Sith Lords: Prima Official Game Guide
- Jedi Academy Training Manual