Thelgrun might have promised Wilted he would provide her the support of the army, but he was honestly skeptical. He continued to observe the battle in the sky as his troops stayed defending the walls. After one day, the four outworlders were still there tussling with Leviathan. Then only did Thelgrun think maybe Wilted's claim wasn't hot air after all. He started sending orders to his commanders to prepare for a full advance.
After one day, most of the wilderness monsters summoned by Wilted were killed. They were unlike the army, who could coordinate and retreat when they were in danger so they could recover. They just fought until they died. Hence, they didn't last too long. Even so, they gave the defenders a chance to regroup and gain better footholds.
