Ghelmer was a quadrupedal demon who resembled a dragon with a skeletal frame. Bony vertebrae-like protrusions jutted outward from his spine, forming a row of spikes down his back. He possessed clawed hands, ears shaped like bat wings, and a tail which was once a fellow demon with a slug-like appearance. He had an all black color scheme which was juxtaposed by the white pupils of his dark eyes. Upon being expelled from Devilman's body, Akira took note that Ghelmer had been rendered rather "scrawny" in appearance due to the water in his body being evaporated by Devilman's flames.