Alastor is a slim, dapper sinner demon with beige-colored skin, and usually has a broad smile full of sharp, yellow teeth. with standing at approximately 7 feet.

He sports a pinkish-red cropped, angled bob-cut with black tips at the ends and two large, black tipped tufts of hair extending from the top of his head, evoking the ears of a deer. The style has an undercut at the back, and two small black antlers protruding from the crown. Alastor's eyes have dark-red sclera, bright-red irises.