Bujilli padded over towards the newfound door. He intended to cast his Listen To Walls spell. It seemed like a good way to find out what was back there, without falling afoul of murder holes, pit traps or worse. He'd heard about a massive pendulum-blade that had been set-up as a trap in one of the buried monasteries back home. Three would-be thieves had been slashed in half before the rest of their party could escape. Too bad his uncle had been one of the lucky ones that day.
He took a deep breath. The tulwar rested smoothly in his calloused left hand. The Gloomlight Glyph hovered at his right shoulder. He reached out to touch the--
A horrid-smelling cloud of vapors roared through the gaping hole of the doorway before him.
Bujilli backed away from the roiling, coiling gasses pouring into the chamber.
His eyes burned and his lungs itched. He coughed. The stuff was foul. Disgusting. Unclean. Bujilli spat but the taste wouldn't leave his mouth. There was something wrong about this cloud of vapors.
He tried to remember what he had read in his uncle's books about such things.
His spine felt like ice--he knew what this was--it was a miasma. A pestilent cloud that spread terrible diseases and plagues.
Something entered the chamber. It buzzed and clicked excitedly. The way that insects tended to do right before they eat some other insect...
Here's the map so far: