Blacklands

Death, and all that connects to it. That is what the Blacklands represent. As much as life and creation are needed so is death needed for mortality to exist. The blacklands are therefore a place of rest and unreast where the dead gather, to wait for Fe´Jasks  reaping.   The Blackland where ultimately not as extremely shifted towards its nature, being in balance with its other counterparts, but the skewed balance that appeared forced the 3 planes further into their extremes. This made the blacklands into the truly dark place it is now, filled with death and undead as all sudden overly big amounts of souls have need to wait for their reaping. This combined with conceptualized failure of souls in form of Aetherials changed the blacklands to be ... strange, and dangerous. 
The blacklands are a place that chokes life, grinding down upon it ever so slightly, but unerringly. While senseless undead wander these lands, shades of lost lives, the souls that wait for their reaping may be driven to take on such wandering forms in a plead for substance. In such cases true undead are born, that wander these lands for varying amounts of time, before their undead nature is grinded down into true death again, where they then return to expect their reaping. Souls, residing within the blacklands, seem to be able to turn into undead more than once but the cause, limit and prerequisites are unknown.

Type

Dimensional plane