Savage Opress was once a common Nightbrother whose fighting prowess impressed Asajj Ventress. Transformed into a monstrous warrior by Mother Talzin, Opress became Count Dooku's new assassin and secret Sith apprentice. His loyalty, however, remained to Talzin. The Nightsisters leader gave Savage a new quest: to find his brother, Darth Maul, who had somehow survived his apparent death and was living in exile in the Outer Rim.
After Dooku was forced by Darth Sidious to dispose of Asajj Ventress, he turned to the Nightsisters to deliver a new apprentice. Dooku was a cruel master to Savage, attempting to hone his apprentice's rage into a powerful weapon.
Asajj Ventress hand-selected Savage Opress from a group of Nightbrother contenders that also included Savage's brother, Feral. Surviving the brutal culling process, Savage did what he could to spare his brother harm, and in the end willingly submitted himself to Asajj's rule if she agreed to let Feral go free.
Mother Talzin led the Nightsister incantations that magically transformed Savage Opress from a wiry Nightbrother warrior into a hulking monster of the dark side. Talzin also ensured that Savage's ultimate loyalty would remain with her.
The Nightsisters of Dathomir ruled over the Nightbrothers, selecting specimens like pets to do their bidding.
Mother Talzin's last task for Savage Opress was to seek out his brother, who lives in exile in the Outer Rim. Savage believed his brother, Darth Maul, was dead... but Mother Talzin knows otherwise.