After building a new War Moon to host his gladiatorial battles, Mongul captured and imprisoned the Justice League. Mongul then forced Hiro Okamura, also known as the Toyman, to create a group of robots to combat the League, each specifically designed to exploit their weaknesses. Unbeknownst to Mongul, Toyman built a fail-safe trigger which merges them into a single, massive mech robot. Batman discovered the trigger and the Justice League escaped War Moon in the newly formed Fulcum Abominus.
