A Gloom Prism is a Necron artefact that can be carried by Canoptek Spyders, Canoptek Tomb Stalkers and Canoptek Tomb Sentinels. A Gloom Prism takes the form of a green crystal laced with arcane circuitry that can generate an anti-psychic null field. This in turn creates a zone approximately fifty metres in diameter that is shrouded from all Warp-spawned powers. The Gloom Prism produces this effect by severing the connection that daemons and psykers have to the Immaterium through an unknown arcane technology.