Return of Reckoning

Hi,

I have question to the greenskin t4 epic quest line "Time to Waaagh!".
We did the questchain up to Step 6, where we had to kill "Slayer Grayoath" at location 50.8/30k in KV.
But we couldn't find our target, we searched the whole area but with no success.

Does anybody know how to find that slayer, or is it a bug ?

Mobs sometimes spawn within world objects or underground. Asking a GM for help or checking again after a server restart usually solves this.