The thunder rumbled ominously above the advancing squads, amplified and echoed by the steep mountain walls that crowded them in on all sides.

Although the corruption was much weaker in Thunderpeal Mountain, the three squads did not ease up their guard. Rather, they were even more cautious than ever, on the lookout for whatever had taken down the missing squad. None of the students who had made it here were weak or foolish by any measure. They were the best of their schools, elite students that had survived and honed their skills through many battles and other dangers.

The fact that one squad had disappeared was a huge worry for all of...