He agreed to work for Darkseid in exchange for power, but Darkseid had him killed once his purpose was completed, leaving him stranded on a desert island where a nuclear bomb was set to go off.

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"He agreed to work for Darkseid in exchange for power, but Darkseid had him killed once his purpose was completed, leaving him stranded on a desert island where a nuclear bomb was set to go off." - It's unclear which 'he' this sentence is referring to - Mannheim, Toyman or Toyman's father. --Irrevenant