Null Rod

Source: Codex: Daemon Hunters, p. 18

This obsidian rod perpetually crackles with anti-psychic energy, nullifying the warp-spawned powers of the Daemonhunter's enemies. It counts as a power weapon. No psychic powers whatsoever may affect the character with this item or the squad he has joined, regardless of source. However, the character with this item and the squad he is with may not use any psychic powers of their own.