The ambush was very successful, from Lancelot's surprise attack to the end of the battle, the total time used was less than a minute. After the soundproof barrier was removed, the noisy sounds from outside the door came back in again, clearly the remaining guards inside the fortress had not realized the battle here and were still desperately preparing for their last stand.
After gathering their equipment, the group left three corpses behind and carefully walked out of the barracks. Outside the room was a circular corridor, with an open courtyard in the middle. Looking down from the edge of the corridor, they could see they were on the third level of the fortress, and each level of the corridor was lined with dozens of Frost Giants holding javelins and throwing axes.