Primal Shadow can be obtained by combining 10obtained from voidwalker-type Outland mobs.
Prior to patch 2.1 Mote of Shadow also dropped from demons, especially mobs at the various "forge camps" and "invasion points"; however it was decided this made Primal Shadow far more common than Blizzard intended. Therefore a change was made so that only the void-type creatures of Outland would drop Mote of Shadow.
Primal Shadow may be transmuted into Primal Water, and vice versa. This is learned via a discovery, which occurs when doing other transmutes.
Primal Shadow is used in the following recipes: