That adventure when the Lovecraftian underpinnings of my setting become horridly all too apparent. The most number of Cope rolls in a single session, and somehow even the two NPCs managed to survive (Wayward Pines + Shudder Island + Green Inferno + Prince of Darkness) in the Drivers' Isles archipelago. After action debriefer received a psychic burst-imprint of what the PCs had experienced, and they nearly went insane.
Good times: five out of five digits. 0,o