At the end of '
Arthas: Rise of the Lich King', it stated that Arthas killed off both his last bit of humanity and Ner'zhul's remaining spirit, so Ner'Zhul is DEAD at last.
In fact we must distinguish between two distinct things:
- On the one hand, the corruption caused by the Burning Legion (Ner'Zhul) through Frostmourne that makes madden to its owner.
- And in the other hand the ability to control the Scourge through the Helmet of Domination.
The new Lich King, aka Bolvar, just inherit the Helmet of Domination but not Frostmourne, which is destroyed. That means that the new Lich King has full awareness of his actions and he has not changed his way of thinking. For this reason, it's funny to me that some of you not feel anything right knowing that the new Lich King is the second most important hero of the Alliance after the King, which clashes with the supposed neutrality that has to have the Lich King.
As for the reappearance of Bolvar and his Scourge at the future, I do think that he will return in a few expansions later, as I already said: