Nether Void
The Nether Void was a planar void where Leshrac, Kristina of the Woods and Taysir fought during the Summit of the Null Moon.
If Planar Voids are in fact planes without worlds in them, then the Nether Void was one of the 12 planes inside the Shard. However, it is equally possible that the Nether Void was the same place as the Abyss.
(Source: The Account of the Summit of the Null Moon (comic))