Two nights from the start of the arena, Aang will find himself alerted by the unmistakable sound of falling rocks - accompanied by loud cursing. In the rapidly falling darkness, Thorin did not catch the tripwire until his boot had already hit it; but luckily, his reflexes, honed by years and years of hard travel and constant state of alertness, throw him to the ground in a rolling dive... which, he finds, was deeply unnecessary as the amount of rocks would hardly have been enough to hurt anyone.

He dusts himself, grabs the wooden branch he's been using as both weapon and shield, and stalks forward, calling out loudly:

"Whoever inhabits this cave, show yourself!" Though wary, he doesn't think the person who set the tripwire aims to harm, and frankly, he doesn't desire a needless fight, either.