"Ah, right. Sorry, long day." Frisk shakes their head, trying to clear away the fatigue-induced fog. "Long story short, because humans are terrible, they trapped a race of monsters under a mountain and sealed 'em in there with a barrier. A friend of mine back home told me he had a plan to free them when I fell into the cavern, and considering how terrible life is down there and how... okay, to be fair, some of the monsters are pretty high-grade jerks, but nobody deserves to look up at night and see nothing but rock."