Death Hollow
this was the term used by the Korunnai to describe any deep well or pit where toxic gases, roiling from the open caulderae of the many active volcanoes on the surface of Haruun Kal, could collect before they reached the "ocean" of the planet's surface. Any creature that fell into a death hollow literally drowned in the toxic gases. Usually, death hollows were camouflaged by lush foliage, so many creatures simply fell in by accident or tried to feed on a tasty blossom and tumbled to their death.