The new design.
Sleens are slow-moving, lizard-like, non-sapient creatures native to the swamp planet of Dagobah. They are omnivores, and their diet includes small insectoids. Preferring damp, dark environments, they would hunt in swamps and forests and return to rest in hollowed out logs or holes dug in the ground.
During the Great Galactic War, Sleens were found on Dromund Kaas.
Behind the scenes[]
The original "design".
The Sleen originally looked exactly like a Monitor Lizard from Earth. That's because a real life lizard was used to portray it in the movie The Empire Strikes Back. However, they were redesigned for The Old Republic—they were made far larger and given many sharp teeth.