Revest attends Class 3-1 at the Demon King Academy. He started out genuinely kind-hearted and went out of his way to avoid hurting people—he wouldn't even develop his Gyze or learn offensive magic. That all shifted when Meno taught him that the Demon King used his power to protect others. The realization hit hard enough that Revest developed serious respect for the Founder, became a dedicated Royalist, and basically became way more confident and arrogant as a result. That said, he hasn't completely shed his original gentle nature; it's still in there underneath the attitude.
Content compiled by AnimeList.moe from publicly available sources.
