He is a horse who have a Headslug pet on his head, and also an astronaut. Tan has a ability to turn BUFF! and in that buff state his VERY powerful, and unstoppable. In his normal form, his just a horse, nothing special, but went his buff state he is VER  BUFF! there no clue why he can able to turn buff but we know is "don't mess with tan horse" apparently...

Trivia:
-tan horse is based on a AMONG US April fools update where everyone is a freaking horse.
-tan horse cannot talk.
-Unstoppable.