The Dark Forest

The Dark Forest is the plane where souls depart to once they die, set to forever drift amidst an unending forest filled with dead trees and a dense fog, blocking out any sun that may or may not exist on this plane.
The souls of the dead can be spoken to here, and in rare cases retrieved. All you have to do is think about someone you've lost in the fog, and they'll appear before you.
Echoes of the past constantly tug at the corners of the fog, whispering into the ears of any living creature that has decided to traverse its depths. Many mages have walked in this forest, entering it as easily as they would transport to any other plane of existence. Some, for knowledge; others, to speak to lost loved ones. No matter what, every single one returns saying the same two things.
The souls of the dead are at peace.
And the Mother takes care of them.
Who the Mother is? No one knows. Dead men tell no secrets.