Breath of The Devourer

For as long as creatures have lived in the Underdark they have spoken of the strange phenomena known as the Breath of The Devourer. It has no known origin, it comes and goes at random, and it is always accompanied by horrid monsters of Deep Iskudar. It is said to be preceded by a mass fleeing of animals in the region, even mighty beasts like The Purple Worm or Umber Hulk are frightened into flight. Their old animalistic senses warn them of The Breaths arrival. Then it rolls in like a thick putrid fog; a heavy green gas that clings low to the ground before quickly rising until it reaches the tops of caverns from the bottom of ravines. It's smell of rotting meat is so potent that the stentch visably ripples in the air around the gas. Those caught in the breath are poisoned by it's potent smell causing them to fall prone and retch up food and bile. It is futile to crawl away, as nothing is constiutional enough to regain composure once they are over taken by the gas. But a slow death of suffucation is not what comes to creatures caught in the smell of the breath, no. They are taken by what comes next. Hunched creatures obscured by gas and darkness, slowly dragging away sentient beings, unable to scream due to the constant vomiting caused by The Breath. Some are devoured on the spot, even as they lay poisoned. No sentient creature is spared, no one to tell the tales of the creatures that follow the the fog. Many speculate, abyssal creatures, unknown abberations, or perhaps a new type of creature yet undiscovered. Regardless, the breath as inspired a saying amongst those who dwell in the Underdark. "When even the monstrosities flee, so must we."