Gantok

Gantok was a humanoid who worked for the Silence.

History
Gantok wore Viking-style attire, along with the Eye Drive worn by many servants of the Silence. He was an avid player of Live Chess. He was rather proud of his skill at the game and, when the Doctor had beaten him during a match, Gantok offered to pay anything to escape. He told the Doctor that Dorium Maldovar knew many things about his death. Gantok helped him get into the Seventh Transept, where he turned on the Doctor. He was killed when he stepped on a booby trap that dropped him into a pit filled with the skulls from the Headless Monks, which proceeded to devour him. (DW: The Wedding of River Song)

Behind the Scenes
Counting spitfire pilot "Danny Boy," whom Gatiss provided only the voice for, Gantok is the third character to be played by Doctor Who writer Mark Gatiss. The other was Professor Lazarus.