Octavian (The Time of Angels)

Father Octavian was a Bishop Second Class who had deployed Doctor River Song on a covert mission. This led to her presence on the Byzantium, which housed a Weeping Angel.

Biography
When Octavian arrived with his clerics at the crash site of the Byzantium, he was displeased with River, until she introduced the Eleventh Doctor, the "equivalent of an army" she had apparently promised for assistance.

While discussing their plan of action, Octavian asked Song whether she had informed the Doctor of her true identity.

He led his men into the Maze of the Dead below the Byzantium. Three were soon killed by the Angel. The Doctor assured him they could not have been saved, but Octavian reminded him that he would be the one to tell their families while the Doctor went off in his little blue box. Nonetheless he still told the Doctor he had faith in him when they were surrounded by Angels. (DW: The Time of Angels)

After entering the forest vault, he claimed River and he were engaged so he could accompany the Doctor and her to the flight deck. On the way he revealed she was in his custody. At the flight deck, when River had already gone through, he was attacked by an Angel. With the Doctor looking at it, it was frozen, trapping Octavian in a headlock, before it could kill him. He told the Doctor that River had killed a man who was "a hero to many", but whose identity he felt unwaveringly the Doctor "[doesn't] want to know." He warned the Doctor not to trust her. The Doctor refused to leave him, but Octavian told him to go, glad that his courage had not deserted him in the end. When the Doctor said he wished he knew him better, Octavian replied that the Doctor knew him at his best. He was presumably killed by the Angel as the Doctor left. (DW: Flesh and Stone)