Originally Posted by
Sukk
In the Book, Arthas (a Death knight) was getting manipulated by Ner'zhul (The Lich King). They shared the same body after he put on the helm and armor and what not. Eventually Arthas' spirit got rid of Ner'zhuls and he became the one and only Lich King. So while Arthas started off good, he got manipulated and basically started enjoying being so powerful and decided that he wanted to become the Lich King. Bolvar still only wants to do good by keeping the undead in check, but give him time, we might have him as a raid boss in a few expansions.