Lords
High Sorceress
0-1 Keeper of Secrets
Druchii Anointed
Heroes
Noble
Sorceress
0-1 Aspiring Champion of Chaos
Core
Dark Elf Warriors
1+ Devoted of Slaanesh
Shades
Maraurders of Chaos
Daemonetters of Slaanesh
Special
Dark Riders
Cold One Knights
Mounted Daemonettes of Slaanesh
Warriors of Chaos
Rare
Spawn of Chaos
Repeater Bolt Thrower
0-1 Knights of Chaos
The Army General must be a High Sorceress, or a Sorceress if no High Sorceress is present (even if they do not have the highest Leadership in the army).
The Army General must have the Mark of Slaanesh.
Daemons cannot join units of Dark Elves or Mortal Chaos.
Dark Elf characters cannot join units of Mortal Chaos or Daemons. Aspiring Champions cannot join units of Dark Elves or Daemons.
Dark Elves with the Mark of Slaanesh still have hatred of High Elves. Units or characters with the Mark of Slaanesh and riding Cold Ones are still subject to stupidity.
Sorceresses with the Mark of Slaanesh must use the Lore of Slaanesh, and gain +1 to cast their spells.
All rules for Mark of the Dark Gods (pages 46-47 of Hordes of Chaos) apply.
Dark Elf characters with the Mark of Slaanesh may take any 'Models with Mark of Slaanesh Only' magic items from Hordes of Chaos as part of their Magic Item allowance.
Any Dark Elf unit that has the Mark of Slaanesh and access to a Magic Standard may choose to take the Rapturous Standard (from Hordes of Chaos) instead of another Magic Standard (although of course only one Rapturous Standard may appear in the army).
Chaos characters and units may not use Dark Elf magic items.