Over the past few months, readers have followed along as the alternate Reed Richards known as the Maker escaped his prison in the primary Marvel Universe and remade his own in the form of an all new Ultimate Universe. For all the Maker's efforts to keep heroes from coming into prominence, he could not foresee the few who have still risen to oppose his machinations.
Source:https://www.cbr.com/ultimate-avengers-battle-important-loss-marvel/