From Lexicanum

The Ether Lance is a Daemon Weapon.

Overview

The Ether Lance is a gateway for warp power to surge into the materium and can be highly potent in both combat and at range. Bolts of deadly warp energy leap from the weapon over a wide area or lure enemies into the lance itself, utterly consuming them with warp energy.^1-p19

Source

• ¹:Codex: Chaos Space Marines (3rd Edition, 2nd Codex), p19