This was a strange idea, taking a character who is already an animal and then transforming them into a pony XD but here we have Amarterasu from the game Okami!
She still has her shield, and her mark is a paintbrush - what else could it be? She uses it to fight evil and change the world. [I still need to finish that game... Heh.]
For the Pony-fied challenge.
Reference pic [x]