[@KawaiiKyouko]

Genghis Khan is legitimately scary, so that works. As far as the horse itself goes, its strength could be a step below a Phantasmal Beast, although actually making it a Phantasmal Beast might be justified, especially since A+ seems to be the rank where Phantasmal and Divine Beasts can be used as mounts.

Riders also have Magic Resistance as a Class Skill, normally, but it might be low since Genghis Khan was around during the Age of Man.