A species of red-skinned humanoid reptilians from the planet Kalee in Wild Space, the Kaleesh had two yellow eyes with slit pupils, that perceive color differently. Although all of their facial features were reminiscent of bats, such as their elongated ears and flat noses, they usually wore masks to hide their faces. Tusks protruded from their lower jaws, with shorter ones on their chins. Kaleesh had a keen sense of smell and could smell death and the origin of an individuals. They had long, thin arms that ended in four-fingered claws that extended from their hands with two opposable thumbs, they were digitigrades, walking on their toes rather than their entire feet, and they possessed a brain, a heart, and lungs and liver. Their internal organs were extremely flammable.

The Kaleesh were primitive people and known for their lack of mercy. They freely appropriated the spoils of war and took what they wanted from the conquered before returning home. Kaleesh warriors traditionally wore fearsome masks, smudged with karabbac-blood warpaint lines above their eyes, carved from the skulls and bones of predatory animals of either a Mumuu or Erkush, one of the few fearsome animals from their homeworld. Their mask were used in battle. If it were discovered that someone wore a mask just for effect, the Kaleesh would not tolerate it. Kaleesh also wore cloaks, head wraps, and used weaponry such as swords, shields and Czerka Arms Outland rifles, a slugthrower.