In the Warhammer 40,000 universe, Cult Warbands are groups of Chaos worshippers united under the influence of the Dark Gods. These warbands often form from disillusioned citizens, rebellious governors, rogue psykers, and defected Imperial Guard units, starting as small cults that grow in power and influence. They worship one or more of the Chaos Gods—Khorne, Tzeentch, Nurgle, or Slaanesh—and their goals include spreading chaos and corruption throughout the galaxy.
Cult Warbands vary in structure and leadership, often led by powerful Chaos Champions, Sorcerers, or Daemon Princes. Their activities range from conducting raids and insurrections to destabilize Imperial worlds, to engaging in unpredictable and diverse battlefield tactics. Warbands dedicated to different Chaos Gods employ distinct strategies: Khorne warbands focus on bloodshed, Tzeentch on sorcery and manipulation, Nurgle on spreading disease, and Slaanesh on excess and hedonism.
The impact of Cult Warbands on the galaxy is significant, as they pose a constant threat to the stability of the Imperium. Notable warbands like The Purge (dedicated to Nurgle) and The Flawless Host (followers of Slaanesh) exemplify the diverse and dangerous nature of these groups. Cult Warbands weaken planetary defenses and morale, often serving as precursors to larger Chaos incursions, and their ability to corrupt and recruit from within makes them a persistent and insidious menace.