Here is what the Death Knight article on Wikipedia says about Shan Nikkoleth:
The Shan Nikkoleth article on Forgotten Realms Wiki does not really give much more:Death Knight article on Wikipedia wrote:Shan Nikkoleth, a Death Knight of otherworldly origin, used to reside in Hellgate Keep (The Savage Frontier, page 42) but was blasted when the keep was destroyed.
The Grintharke article says that Grintharke is a balor and that "he and his followers were exiles from the Abyss". The Grintharke article is in the Inhabitants of the Abyss category, but the Shan Nikkoleth article is not.Shan Nikkoleth article on Forgotten Realms Wiki wrote:Shan Nikkoleth
Shan Nikkoleth was a death knight commander of the varied armies of undead, cambions, and demons in Hellgate Keep.
For his lord Grintharke, this powerful death knight led and directed many patrols. Many of these patrols scoured the wilderness for treasure for their master and the Keep. Due to this, Hellgate Keep became a house for the treasures of many lost realms.
Much like his master, Shan was reputed to have an other worldly origin.
So where does Shan Nikkoleth come from? Is he a Death Knight created in the Abyss or did he come from another world on the Material Plane?
Did Grintharke meet Shan Nikkoleth in Hellgate Keep or did they meet on the Abyss or Shan Nikkoleth's homeworld?