The artifact reserve is a protoss structure used to store artifact fragments and reassemble them. In an alternate timeline where Zeratul survives the beginning of the End War, Zeratul used these reserves to store fragments of xel'naga artifacts to empower his forces.
The artifact reserve is the structure Zeratul uses to store any artifact fragments he discovers in Co-op Missions. The structure serves as the focal point for stasis beam, but otherwise serves only as a visual way to track the number of artifact fragments obtained. The artifact reserve is invulnerable.
Protoss Units and Structures of StarCraft II
Versus units and structures
units and structures