When the sun was rising, Aion finished his work of getting rid of all the evidence. During that time, somehow, Arc managed to convince the thirty thousand souls that were killed to help Aion. He was trying way harder than Aion had expected, but not in a suspicious way... probably.
Also, during that time, Aion realized that he couldn't just wait for the enemies to do whatever the hell they wanted… he had to strike them back, but it was clear that they would be waiting for him. Even if he ignores them, he has to consider how he is going to find them…
"Arlana probably knew that this was going to happen… she doesn't want to change things that are bound to happen that much, but she should be easily convinced that I can't just wait for the enemies to come and do whatever they wanted," Aion thought once he began to fly home.