Jata

Jata was an Osumaran.

Jata left Osumare in an alnitak class Q7 starship. In 1899, he crashed his ship into Earth. Clint Currie found Jata in the Wyoming desert. Deciding to "make the best of [the] barbaric world", Jata helped Currie commit crimes. Jata became the mastermind behind a number of big-time hold-ups and robberies. Because the black star on Jata's forehead was unique on Earth, Jata was put on wanted posters that identified Jata as Currie's horse.

Three months after Jata came to Earth, the Twelfth Doctor found his crashed spaceship. He came to town a town that Currie's gang were committing a robbery in. While Currie's gang were robbing a train, the Doctor came to the tree which Jata was tied to. Jata willingly came with the Doctor and the Doctor left a regular white horse with a black star painted on its forehead in Jata's place. When Currie tried to consult the horse on how to escape from the town's sheriff, the horse didn't reply because it was a horse and Currie was caught.

The Doctor then took Jata back to Osumare in his TARDIS. (COMIC: From the Horse's Mouth)