From Lexicanum

The Bedlem Staff is a Daemon Weapon of Tzeentch.^{1-p59 2}

Overview

Bedlam Staffs originated during the Horus Heresy from within the Thousand Sons. Since they turned to Tzeentch the Bedlam Staffs have been held by many warriors and are steeped in their psychic remnants. When they strike, Bedlam Staffs remove all thoughts from the minds of the target, making them pause temporarily.^{1-p59 2}

Sources

• ¹:Codex: Chaos Space Marines (3rd Edition, 2nd Codex), p59
• ²:Warhammer 40,000: Wargear