When you say generic vampire lord, do you mean actual vampire, or a kind of glowing wight king? If it's the former, have you activated the MCT (Mod Configuration Tool - one of the required mods)?
If it's the later, see ProfessionalProcrastinator's answer bellow.
Warpstone gets generated at random every turn when you got a warpstone mine.

In the Campain you have to capture the black pyramid and then raise it( I don't mean destroy it) by pressing the acesend the black pyramid next to its name. this will cause skaven to spawn and nagash to be replaced. survive 5 turns and Nagash's true form will spawn.

Hello the mod is beautiful and I was waiting for it so long, I gave all my steam points I had to reward it. But the problem is generic Vampire lord instead of glowing wight king, especially in multiplayer my friend has same issue. If you know it will not effect game and we steel can summon Nagash by taking his pyramid cool, i will just think it is bug.

Assume the mod won't work in MP, it's script heavy, and MP games don't like those unfortunately.

I'm assuming there is suppose to be a button on the panel of the "black pyramid of nagash" ?. I have it captured and everything but I cant seem to find a Acesend button or anything else to get anything to trigger. Everything else seems to be working fine. turn 56 I have a few other mods so i'm sure that's my issue. most are 90% visual stuff. Love this mod. and I'll play it out with Neff and Archon happily just wanted to see if im stupid and missing somthing

Found it. damn is it small and in a place i would have never guessed. for anyone else having issues. its next to where landmarks and trade items appear off to the side on the actual campaign map.