Let 'Volir is the head of a mercenary Sangheili clan and shipmaster of the assault carrier Enduring Conviction, the most powerful warship in the Banished fleet.
Atriox engaged The Shipmaster's forces to bolster his Banished army and provide the aerial advantage and firepower that the Banished were lacking; the Enduring Conviction can be called upon to unleash orbital plasma bombardments to support Banished ground troops or to destroy or damage enemy structures.
His decision to bind his crew to the Banished has forever tarnished his name in "proper" Elite culture, but the Shipmaster knows that in the current chaotic state of the galaxy "proper" is a luxury not all can afford if they want to keep their crew and their ship intact.