"Hero robot" is what the Thirteenth Doctor called a bejeweled robot that was owned by the Hoarder. Originally polishing a mirror, she reprogrammed it with her sonic screwdriver. It polished the lock off a door and saved lives of the alien children the Collector had kidnapped. She took it on board the TARDIS because she felt it deserved better than being locked up by the Time Agency as evidence. (COMIC: A New Beginning)
