The Ulk-Ra were a species native to a wooded planet with copper-sulphate oceans. They evolved from an arboreal species.
At some point in their history, some Ulk-Ra were removed from their planet and tested by the War Lords for possible use in their War Games. The Ulk-Ra were rejected for the games and sent back to their planet after being modified by the War Lords. (PROSE: War Crimes)