A working name for a multiverse that adjoined Seth’s Multiverse A before the Puncture. Some event in Multiverse B caused the Puncture, and as a result the Material Planes and much of the rest of Multiverse B disappeared. The metaphysics and cosmology of the multiverse survived, however, and replaced those of Multiverse A.
According to the shadar-kai, Multiverse B contained a world called Kadderash that was the origin of the Puncture. If their account is true, the souls on Kadderash must have irrecoverably vanished during the event.