Karu-Sil was born on Graxos III. At a young age, her family was slaughtered during a raid on her home. After several days, she wandered into the jungle in search of food. She was taken in by a pack of three fearsome beasts, who hunted with her and raised her as one of their own. Wanting to look more like them, she altered her appearance by sharpening her teeth into fangs.
One day, Karu-Sil and her pack found a village by a river. There, she saw a boy, who approached her. She attacked him, and together with the beasts, killed him. They were found by Blish, the sector's Green Lantern, who killed the beasts, thinking that they had also been trying to attack Karu-Sil. She was sent to an institution on Graxos IV, where she killed one of her psychologists.
Karu-Sil was freed from the institution when she was chosen to represent her sector in the Sinestro Corps. She frequently used her power ring to make constructs of the three beasts she had grown up with.
