Spiked Corridor is locked, and Torture Pit is unlocked.
({3} magic symbol) ({R} magic symbol) available.
Steps
Unlock Spiked Corridor by paying ({3} magic symbol) ({R} magic symbol) , triggering it and Ghostly Dancers' second ability.
Resolve the Spiked Corridor trigger, creating three 1/1 Devil creature tokens.
Resolve the Ghostly Dancers trigger, creating a 3/1 Spirit creature token.
Activate Thermopod's second ability four times by sacrificing the Spirit and Devils, adding ({R} magic symbol) ({R} magic symbol) ({R} magic symbol) ({R} magic symbol) .
Marina triggers four times, and each Devil triggers once.
Resolve all Devil triggers, dealing 3 damage to any target.
Resolve all Marina triggers, untapping it.
Activate Marina by tapping it, locking Spiked Corridor.