The Primal Stone is a gem that is connected to the Primal. It's Garrett's and Erin's main objective in the prologue, The Drop, and first seen when the baron tries to harness the Primal with a ritual described in an ancient tome. During the following disruption of the ritual the stone breaks into four parts, each of them still containing Primal energy.
The first piece is brought to the baron's Keep and stored in the great safe to reduce its negative influence on the City, the second part is used as the power source of the experimental reactor in the underground laboratory of Northcrest Manor, the third piece is taken by Orion and becomes part of his pendant while the final fragment resides in Garrett's right eye.
During the course of the game Garrett has to collect all fragments to free Erin and save the City from the Gloom.
- While the Primal Stone contains Primal energy it's unclear if it possessed it from the start or if the gem is simply the baron's original vessel.