The Red Lady calls from inside the mountain. You and your friends hear her screams during the night. The other children don't. Together, find answers at the mountainside. Describe why you choose to investigate. In secret, choose a friend you want to PROTECT. You find an opening. As you descend, it collapses behind you. FIND AN EXIT. The Red Lady watches from the dark, singing temptations through her unhinged jaw. Sentient traps, gruesome puzzles, and unfathomable magics scar the underground city. You start with 2 Fear. When doing something difficult, roll d6 equal to your Fear. If throwing someone, roll d10's instead. If you roll any 1's, everything worsens; you gain one Fear. Otherwise, you succeed. If you roll two or more 1's, the Red Lady crawls from beyond, her jaw twitching sporadically. Either You are TAKEN by her. Or If a friend succeeds on a roll to throw another friend towards her, they are TAKEN in your place. Those TAKEN become the Red Lady and may speak through her in temptations, trying to make players betray each other. If two remain, and one PROTECTs the other, they escape the cavern together. Else, only one can escape alive.
To play this the GM will probably have to prepare some content for the players to explore. Don’t expect betrayals to come immediately, they are the payoff after building up in tension over the course of the session as players discover their characters. This game requires good players and a good Gm. For the lazy GM, you can just Frankenstein together dungeons from Dungeons and Dragons modules to create the underground city quickly. Be sure to reward player ingenuity.