The Mark of Chaos refers to the physical and spiritual changes which a Chaos God might choose to bestow upon his most favoured servants. Along with the actual physical, symbolic Mark of the Chaos God or of Chaos Undivided, the bearer becomes a Champion of Chaos, a recognised servant devoted for the rest of his existence to championing the cause of that Dark God in the mortal universe.
Chaos Space Marines and other servants of Chaos can either worship all four of the major Chaos Gods in all their glory as Chaos Undivided or dedicate their lives to just one of the Ruinous Powers. Each path offers its own rewards.
Mark of Chaos Undivided
The Mark of Chaos Undivided is a glyph given to a follower of Chaos who devotes him or herself to all four of the Dark Gods equally. While the prayers of a mortal devoted to Chaos Undivided may be answered, they are unlikely to receive the special gifts that come from worshiping just one of the Dark Gods. A follower of Chaos Undivided may also honour the lesser daemonic entities of the Warp if they are more likely to help him. Others view Chaos Undivided as a unified whole, the various Ruinous Powers as actually an aspect of a single, unified God of Chaos. They may give their service to one God but are likely to never gain much favour with an individual power. Finally, others seek to use Chaos as a means to achieve their own ends. This is often risky and only two outcomes ultimately exist, daemonhood as a Daemon Prince or damnation as a mindless Chaos Spawn.
Mark of Khorne
The Mark of Khorne is given to those who follow the Blood God Khorne and embrace that Chaos God's particularly bloodthirsty ways. Khornate Champions are fearless and devastating in close combat, they are often possessed of a blood-crazed berserker frenzy and disdain any form of ranged warfare. They hate any form of psychic power or sorcery, seeing it as a form of weakness that kills from afar rather than up close where one can feel the life ebb from one's foe. Khornate Champions are often armed with Chainaxes.
Mark of Slaanesh
The Mark of Slaanesh is a mark that drives the bearer to fulfill Slaanesh's undying hunger for pleasure and new sensations. The bearer is addicted to seeking out new pleasures and is often cloaked in a supernatural glamour that disturbs their adversaries. The most common bearers of the Prince of Pleasure's mark are the Noise Marines of the Emperor's Children Traitor Legion. Bearers of the Mark of Slaanesh are fearless, for even death itself is to be savoured as a new sensation and they possess the Warp Scream ability, in which the individual emits a piercing supernatural cry powered by Warp energies that disorientates his foes.
Mark of Nurgle
The Mark of Nurgle is given to Nurgle's greatest followers and they become a living host to the powers of death, disease and decay. Units of Chaos Space Marines with the Mark of Nurgle are likely to become Plague Marines, gifted with extra bulk and resilience by the Plague Lord, making them much harder to kill. The Champions of Nurgle are horrible to look upon and are a bane to all life.
Mark of Tzeentch
The Mark of Tzeentch is given to the most devoted followers of Tzeentch, the Changer of Ways and bestows potent psychic powers on the bearer. The greatest followers of Tzeentch are the Chaos Space Marines of the Thousand Sons Traitor Legion, incorporeal animated suits of Power Armour who each possess the potent powers of a Chaos Sorcerer and are the greatest champions of change in the universe, despite their own unchanging natures.
Mark of Chaos Ascendant
The Mark of Chaos Ascendant is a Mark of Chaos that is unique to Abaddon the Despoiler, the Warmaster of the Black Legion and of Chaos Undivided. The Mark of Chaos Ascendant is a symbol of the favour the Despoiler, as the successor of Horus, has earned from each of the Chaos Gods as the ultimate Champion of Chaos Undivided. The mark gives him all the abilities and enhancements of the Marks of Khorne, Nurgle, Tzeentch, and Slaanesh. This mark is proof of the fact that the Ruinous Powers have a plan for Abaddon, and as such he is immune to death, for his soul will always be resurrected by the Dark Gods until his purpose has been fulfilled.
- Codex: Chaos Space Marines (3rd Edition, Revised Codex)
- Codex: Chaos Space Marines (4th Edition)