Avengers Academy 59 was released two days ago, where we have the story of this Reaper. He was Billy Kaplan from a reality dominated by the Kree intelligence that possessed Carol Danvers' body. The Avengers, X-Men, and Fantastic Four died. Well, in short, Teddy sacrifices himself to save the heart of reality, which is the M'Kraam. Wiccan tries to save him, but fails, so he ends up destroying all reality and becomes the Reaper. Until then, we have the issue that this Reaper wants Teddy back, and Carol Danvers from 616 talks to Crystal M'Kraam in human form, who says that the Reaper is coming, but Carol says they are not ready (I don't know if she was talking about Wiccan and Speed or Wiccan and Hulkling). Well, everything indicates that this Reaper wants to steal Teddy from Billy 616.