The Staff of Light is a device of arcane technology that serves as both a symbol of rank and a weapon for Necron Lords. As well as projecting devastating blasts of energy, the Staff of Light may also be used in the Assault phase, in which case it counts as a power weapon.
Errata — Chapter Approved: Codex: Necrons Q&A (v2.0): If the Lord upgrades to a Warscythe, the Staff of Light is completely replaced, including its shooting attack.