Devin Levin are memories of a false father implanted in Mrs. Levin and Max Tennyson's minds.
Appearance[]
In appearance, Devin was outwardly indistinguishable from a human. The same is true for Kevin and other Osmosians that are not fully mature and Devin lacks horns on his head (it's possible he has them, but they are hidden in his hair or Osmosians can breed before being fully mature).
History[]
Devin was a false memory implanted by Servantis. He supposedly died in Max's arms. It was eventually revealed though that He was, in fact, false memories put in Max's mind to make sure he kept a watch over Kevin.