As part of Bastion and the Human Council's plan to kill the Messiah Child and destroy mutantkind, a large dome was built over the Bay Area to cut off the X-Men from escape or help. Once the dome was activated, Bastion opened a dimensional portal from a divergent of his home reality to allow in more Nimrod-Series Sentinels. Like the original Nimrod, these Sentinels are able to detect, analyze and adapted to mutant powers. They are also self-repairing. The X-Men were barely able to subdue them, and several X-Men sustained severe injuries. Every five minutes a wave of five new Nimrod Sentinels continued to appear through the portal. Only by sending X-Force, Cable and Cypher into the future to reprogram and destroy the Nimrod Master Molds were the X-Men successful to defeating them.
Bastion was reverting into Nimrod-like appearance and when all the other Nimrods were destroyed Bastion appearance was completely returned to Nimrod form before he battled and was destroyed by Hope Summers.
A fragment of one of the Nimrods found it way to an automated car factory which it used to repair and build a primitive versions of Nimrod. However, this was discovered by the X-Men and a team was sent to destroy it.