This lore can be found by a Knight on Corellia.
A one-time respected member of the Jedi Council and its most fervent advocate for peace, Master Tol Braga now willingly serves the Sith Emperor. His confrontation with that foe showed him the nature of true evil and revealed a powerful force he had grossly underestimated. Master Braga’s failure to redeem the Emperor broke his spirit. With his pride and faith shattered, he succumbed to nihilistic despair. Unlike Warren Sedoru and Leeha Narezz, Master Braga did not require the Emperor’s oppressive domination to remain obedient. He knowingly surrendered to the power of the dark side, believing it was his punishment for allowing pride to blind him to the Sith’s true nature.