You may be of use to me
Yastaful is a disembodied spirit, the only physical manifestation it is capable of is the mystical tattoo it leaves on those it binds to Xins cause.
Yastaful was a rather unimportant spirit than ran into Xin by complete happenstance. Xin had conquered a paradise world, looking for a vacation spot. While swimming by a picturesque cliff Xin noticed a small cave and decided in investigate. It was there that he found Yastaful, bound to the location. He freed the spirit, and in exchange it offered it service in his name.