While still a member of the Covenant, Atriox carried out several suicide missions. However, his growing hatred for the theocratic empire led him to defect and form a splinter movement, renouncing the Covenant religion while doing so.
Atriox led the Banished into several conflicts with the Covenant prior to the Great Schism. The Covenant would eventually come to view Atriox as a threat on par with humanity.
Atriox would eventually lead his forces to take over the Ark a month after it had closed. However, the crew of the UNSC Spirit of Fire landed on the Installation four months after, bringing them into conflict with Atriox and the Banished.
Atriox hijacked the Ark's portal network, allowing him to teleport his troops anywhere in the Ark.
While many of his troops were destroyed when Professor Anders separated the land they were standing on, Atriox survived along with a legion of his forces and began preparing for his next skirmish with the UNSC.