Archibald Angelchrist

Professor Angelchrist helped the Eleventh Doctor defeat the Squall in London, during the year 1910. Ten years after helping the Doctor send the Squall back through the rift, the Doctor, Amy, and Rory returned with Arven, who had been given a new body, and left him to live with Angelchrist. (NSA: Paradox Lost)

Behind the scenes
Author George Mann, who created Angelchrist, has featured the character in several short stories published by Obverse Books, such as The Albino's Revenge in the 2012 Obverse collection Zenith Lives!