Jean-Paul Beaubier and his sister Jeanne-Marie were drafted into Apocalypse's forces as he took over America. As Northstar and Aurora, the twins became members of the Elite Mutant Force that policed Apocalypse's domain.
When Christopher Summers, the father of Prelates Cyclops and Havok escaped captivity, Sinister sent the EMF to capture him before he could cause an infestation of the alien Brood. Northstar and Aurora confronted him and were knocked out when Summers blasted an abandoned fuel truck. His Brood persona almost slew them both when his human persona reasserted itself and he left them. He was ultimately slain by Cyclops.
Much later, the Beaubier twins were dispatched to recapture a group of mutants that escaped from the breeding pens kept by the Dark Beast. Northstar personally slew the mutant known as Newt. Unknown to all at the time, Cyclops was secretly freeing slaves from the pens, and when Polaris had witnessed him freeing others, he later broke her out to maintain his cover. However, he was confronted by Northstar and Aurora whom he blasted into unconsciousness before they could recognize him.
Northstar and his sister were out of commission until the fall of Apocalypse. With the reconstruction of America, and the formation of the Department of Mutant Affairs, the X-Men were officially sanctioned to bring in all those who willingly aided Apocalypse on war crime charges. Northstar and Aurora fled to Canada where they were tracked down and killed by Weapon X and his daughter Kirika.