Gil

Gil was once a human but was transformed into a demon by Kharl. Later sold to Nadils army he was treated like a slave by Shydeman and Fedelta. Despite his hopeless situation he was rescued by a rebel Yokai named Raamganas who took care of him and treated him fairly and whom Gil eventually fell in love with. But the mind control placed on him by Shyrendora enabled Nadils army to toy with him turning him into a merciless demonic beast and in doing so to kill Raamganas. Gil has little recollection of the things he did and he lacks the power to stop it. He later killed his brother Barls wife as well as his niece Fiji. While Gil is one of Lord Nadils prized demons he is also the rightful Dragon Knight of Fire. Later on Gil takes back his title as a Dragon Knight. Source: Wikipedia