A floor trigger opens holes in the walls, and millions of angry bees fly in from all sides. All characters in the area take 1d4 HP damage per minute from stings. Attacking with conventional weapons is fruitless. The bees are too fast to outrun, and will follow the characters where ever they go even if they try. Optional: No time to react before the characters are swarmed! Optional: There might be a large pool of water the characters can jump into, in order to escape. Optional: No AC/Dex rolls/Saving Throws allowed (there's too many bees, and they can get between any chinks in character armor); only magical protections are factored in.