Board Thread:Questions and Answers/@comment-13886763-20160426181210/@comment-24685938-20160501150726

Stryzzar wrote: Didn't he control Gwen until Kevin gave her that helmet?

With these omnipotent beings, they can exist outside the normal realms of reality, possibly outside of time itself. And Diagon not appearing could just be the writers forgot about him. Diagon isn't omnipotent. Gwen wasn't in her anodite form either way.