Many models in this army list have the Mark of Chaos Undivided listed among their special rules. Of those that do, some have the option to replace it with the Mark of a specific Chaos god:

• A model cannot have more than one Mark of Chaos.

• All models within a unit must have the same Mark of Chaos.

• A character with the Mark of a specific Chaos god can only join a unit with the same Mark, with the Mark of Chaos Undivided, or with no Mark.

• A character with the Mark of Chaos Undivided can join any unit as normal.

Note that, with the exception of Daemonic Mounts, the benefits granted by a Mark of Chaos apply only to its bearer, not to their mount (should they have one).