Rhona Mitra has been cast as Mercy Graves for the CW's fourth season of Supergirl, according to Deadline. In what is described as a recurring role, Mitra's Graves has bee repositioned as "an ex-CADMUS agent who has always believed in human exceptionalism."
Just as in comic books, Mitra's Graves will have a connection to Lex and Lillian Luthor, but with the two of them imprisoned, her character will "[step] out of the Luthor shadow" and become "a key figure in National City's growing 'human-first' movement."
Reportedly joining Mitra on the show is Grey's Anatomy's Robert Baker, who will play Otis Graves, Mercy's brother.
Supergirl's fourth season is scheduled to begin October 14 on the CW.