I think, just like with his daemons, you don't get a chance to think about it clearly

Liber Chaotica also makes references to Slaanesh being the "inheritor", the final Chaos God who will usher in a new age and ascend to a new height. It is from a biased source, ofc, and it is Warhammer Fantasy not 40k (though there are paintings of CSM in the book).

Yeah, I remember Liber Chaotica. For those of you not in the know, it was this fantastic awesome book that was written in fantasy universe by the perspective of a wealthy adventurer that was eventually executed for heresy, and his ramblings (that started off completely anti-Chaos but slowly got corrupted) were collated by a witch hunter (or two) who also slowly started to succumb.

The adventurer apparently got sucked into the Realm of Chaos, but was returned unharmed to pen the book and he describes everything he saw. Including 40k elements (as Maledictum says, things like Chaos Space Marines). It's still canon afaik, just like Liber Necrotica or whatever the one written by that Von Carstein chap.

But there are a couple of references to Slaanesh being that inheritor, most notably in Daemons of Chaos army book, but there's the few odd references in Chaos Daemons too. Obviously, only written in the Slaanesh section though.

I didn't think malal was this popular

I vote for the plaguefather!!!

So my choices are:

Become a slavering, barely coherent maniac.
Become an effeminate wastrel.
Become something I can barely recognize.
Or stink worse than the inside of a Dreadnought.

... Undivided, since you're twisting my arm.

Blood for the blood god!!
all other gods shall tremble at the lord and master
of death and violence
we shall drink the crimson wine of life
and bathed in eternal crusade

In my opinion its Nurgle HOWEVER from an in game perspective if they will be giving benefits when choosing a mark its completely situational. For example if you are going to be a Raptor I believe you should go with Khorne to get the combat bonuses, would love to see the game have some similarities to the board game.

Tzeentch... unlike the other gods he has a wardrobe. The other Night Lords will lynch me but if i were still doing models i would be making a Night Lord esque skin for a lord of change >8D
Skeleton bird with blood red bat wings and lots of lightning. =Q_

if Raptors "have to" take mark of khorne in order to be effective something will be wrong.

Nurgle Raptors ftw.

1.Jump in
2.Give everyone AIDS
3.Jump out
4.?????
5.PROFIT!!!