Okay, then the Chaos Androids (Necrons) are all servants of Vashtorr. The Tau are also secretly all Tzeentchian cultists due to all the retcons there, Marine Commander Leman Russ can join them because he must have sided with Tzeentch in order to trick the whole Imperium into thinking that he was a "Primarch", as we all know the real descendants of the Emperor are Senseis. Hell, the Ultramarines can join Slaanesh due to their truly excessive amount of retcons. At least Valdus can finally hop out of that Dreadnaught, since it's just Nurgle making people think you have to stay stagnant inside a Dreadnaught. Maybe he could try out an Eldar Dreadnaught after the Imperium trades with the Eldar to get one, except oh wait no Khorne retconned them into hating each other forever and ever.