There are different assumptions what the Legion of the Damned are exactly:
- Some Astartes that were lost in the Warp and reemerged somewhat changed
- Some dead Space Marines that are given one last chance to do something for the Imperium, aka Saints
- Daemons of the Starchild, i.e. the Emperors representation in the Warp as a God
So, if they are Astartes that were effected by the warp, there cannot be any Primaris Marines as they don't have access to the new Geneseed. However, if they are Space Marines given another chance to serve the empire or Daemons of the Starchild, they could appear as Primaris Marines. So, is there any mention that a Primaris Marine was among the Legion of the Damned or even once consisting only of Primaris Marines.
So, has there ever been a Legion of the Damned Primaris Marine?