X-Men: What Happened To Everyone Who Became The Phoenix?
16. Feron
A powerful mage who traveled to Earth-616 to get himself some of that lovely Phoenix Force, Feron used it to create ancient towers across the omniverse. This formed a permanent energy matrix which was stolen by Merlyn and Necrom.
This caused the Phoenix Force great pain and made Feron feel so guilty that he spent the rest of his life trying to atone.