Zugnaex

In ancient times, the gods imprisoned a demon called Zugnaex to prevent it from annihilating reality. The prison is interdimensional, indestructible, and bound by immortal blood. It is also the case that the prison has one specific vulnerability: if any living mortal speaks the demon's name aloud with perfect pronunciation, every syllable correct, the demon tears through the dimensional boundary, bypasses its eternal confinement, and returns to destroy the human race. Someone has learned the name. Only coordinated effort from you and your allies can stop Zugnaex and prevent what follows. The stakes are as large as they get.