The underworld forces that headed to Aurebor hit the defensive fronts on the second day after the battle in Hydrurond started.
It was Aurebor's Southern defense line that was hit first. The situation was the same as in Hydrurond. The defenders faced the underworld's vanguard army first.
Unlike the battles in Hydrurond, the divine factions didn't come during the middle of the battle. They were present before the battle started. They joined the defenders around the same time the Council of Elpo and the Council of Virtus arrived on Hydrurond's battlefields. Most likely these divine factions moved at the same time after the first contact between the upperworld and underworld forces.
At the Southern defense line, the Verremor army was bolstered by Pride's faction, the Council of Hybris. The members of this divine faction wore white robes that covered most of their bodies, including their faces. When they moved, glistening black armor was spotted under their robes.