The Urdena

The Urdena are the "roots" of Turulsul, the World Tree, which resemble far more the filament extensions of a fungal network than traditional tree roots. However, their scale is large enough that each filament can grow to be a cable as thick as the trunk of a tree, or as thin as a spider's web, continually splitting off to a fractal infinite and microscopic scale. They continually grow through a mechanism not well understood even by the wisest of Uskara, as the World Tree seems to not consume anything, only create. The Urdena leak "sap", a copper-colored metallic liquid, and cutting one of the Urdena can cause this sap to flow quicker, though may also provoke an unfortunate reaction. This sap fertilizes the land, creating plenty where there was none, and seems to be part of some underlying natural cycle in the Uskaran ecology. Much more than the World Tree itself, the Urdena are associated with fecundity and monstrosity. They remain beneath the ground and create monsters (specifically primal beasts) when they engulf flora & fauna. However, they can also be used as a material to produce arcane creatures, and many accursed kindred such as the lamia and medusa, while said to be cursed by the gods, have some involvement of the Urdena in their mythology.
The Urdena continually grow, but they also sometimes retreat or decay, leaving tunnels behind that become inhabited by all sorts of strange life. The Underworld of Chur has greatly expanded in the ages since the germination of the World Tree because of this, growing more and more expansive with each successive World. However, the Urdena never cross the Golling, for reasons unknown. Many occultists speculate that if they were, it would be to disastrous consequences.