Drawn to the Waaagh!: The powerful beat drummed out by a Warchanter draws ever more Ardboys to the fight.
You can use this command ability
if the ORRUK WARCHANTER
from this battalion is on the battlefield when a unit from this battalion is destroyed. If you do so, roll a dice. On a 4+, a new unit identical to the one that was destroyed is added to your army. Set up the new unit wholly within 6" of the edge of the battlefield and more than 9" from all enemy units.