Who is Delton 4 in the play, Visit to a Small Planet?

Delton 4 is a leader of Kreton's unidentified home planet. He is an alien who enters the play at the end, after he is summoned by Ellen Spelding. He explains that Kreton is "morally retarded" and "was able to escape from his nursery." He apologizes for Kreton's actions and takes him home.