- You may be looking for the character from Excelis Decays.
Mattias was the husband of Maria. He was one of a group of humans on the planet Trenzalore who had been gathered by the Eleventh Doctor while the Doctor examined the capsule of ice containing pieces of a sonic cannon near Preacher's Clump. He was later present outside the Clock Tower in Christmas when the Doctor warned the townsfolk about the imminent Ice Warrior attack. (PROSE: Let it Snow)