Dark Under was created when the skravyn were sealed in the tunnels of Nevre. Dark magics seeped out from the sealed portal and creatures in the tunnel were twisted by it. The survivors of Dark Under speak of a darkness darker than black and an oppressive dread. They also say that if you turn around then you may yet survive.
Though most creatures from Dark Under stay below the ground some of them have been seen above the surface. The noxious flyers periodically fly out in small numbers, and every hundred years or so a flight of hundreds razes the surrounding landscape. Gaseous tendrils, gas sacs with tentacles that range from small floating balls to giant lumbering bags of flesh that can no longer float have been known to terrorize small towns. Skittering creepers have replaced many large insects on the surface of Nevre.
In the deeps of the Forest of the Elves, where not even the elves go, the skittering creepers have taken a niche as the apex predator. Every few decades the elves have to push them back or risk the forest being overtaken. The skittering creepers that still live in Dark Under are much more fearsome than their surface brethren. Few have escaped alive from encountering these roaming packs.
– Excerpt from the works of Jergolt, The Scholar