Barnabas

Brother Barnabas of Thetis was a former member of the Brotherhood of Seth from Camlorn, High Rock. He is found dead in the Mines of Khuras.

Background
After receiving a vision that Uriel Septim VII was captured and that only the Staff of Chaos could free him, the rest of the Brotherhood ignored him or accused him of insanity. Desperate to save the Emperor, Barnabas murdered fellow member Brother Martinus and stole a map fragment, hoping it would help him find the location of the Crypt of Hearts.

Mines of Khuras
Senior Brother Halfas Varn tasks the Eternal Champion with retrieving the map fragment in exchange for the location of Crypt of Hearts.

Trivia

 * Other then the Eternal Champion and Ria Silmane, is the only other character in to know the truth about the Emperor and Jagar Tharn's takeover.