Keleath

You right. (The first observed was in Ulgu and the spell was from lore of shadow in wfb. Sorry for my misinterpretation).

Pendulum is linked to Ulgu Geminids are from Uhl-Gysh (The sub-realm where the Aelfs gods imprisoned Slaanesh)

It was already like that when I was there last fall.

In my opinion, a "war elephant" would be better with the Hedonites. It would stay in their Indo-Persian vibe.

Yes, they are canon/lore. For the example I gave about Ogors and the fact that they're prone to joining the ranks of the HoS, you can find the same information in the Ogors v2 battletome.

I disagree. According to the lore (Ogors battletome v2, Soulbound, brokenrealms Morathi…) it's the Hedonites of Slaanesh who should have corrupt Ogors. from Soulbound Champion of Destruction: The method by which they acquire food rarely matters, and many Ogors have no compunctions about accepting work from Sigmar, only to serve in Archaon's armies immediately after. That being said, there are some lines that most Ogors won't cross. Their obsession with eating means Ogors are particularly vulnerable to corruption by Slaanesh, but these fallen hedonists are looked upon with scorn and suspicion by the rest. Mercenary work is one thing, but giving up the Mawpath forever and shackling oneself to a weak god is quite another.

For Khorne, Book II also mentions Korghos Kul, who would potentially reach the status of demon prince (double kit demon prince/named demon prince for BoK?).

Probably Slaanesh. In the celestial tomes for both factions they talk about the havoc Sigvald's decadent host is wreaking on the Ossiarch empire.

In a slaaneshi themed army, with Sigvald as an ally O-)-c

This is not the battalion box. It's the new models (Gardus, Kragnos, Krulghast Cruciator, Warsong Revenant, Be'lakor, the van Denst, Kroak and Dexcessa/Synessa).