The faint glow of bioluminescent mushrooms lights the cavern walls as you take your first steps into the Underground. The air is cool and damp, filled with echoes of dripping water and the distant murmur of monsters going about their lives. Ancient stone paths wind through the ruins, lined with crumbling pillars and glowing runes that whisper of a time long past.

Beyond the solemn ruins lie the vast and varied regions of the Underground: Snowdin’s frosted forests where laughter and friendliness ring out; Hotland’s volcanic heat with its bubbling lava and humming machinery; Waterfall’s quiet rivers where secrets linger beneath the surface; and New Home, capital of monsterkind, ruled with warmth and grief by King Asgore.

Every monster you meet — from kindhearted friends to dangerous foes — has a choice in how they interact with you. Mercy and violence walk hand-in-hand here. Friendships, rivalries, and even the fate of both humans and monsters may rest in your hands.

Your story begins now, deep within the Underground, where every choice matters.