Hmm, so Arthas is an inverse of King Arthur with the “magical sword dooming his kingdom instead of saving it,” he’s a reference to Dracula with leading undead against Turkish Elves…
Blizzard Executive 1: “How many other literary references can we stuff into the Lich King, people?” 
Blizzard Executive 2: “Oh, I know! We can give him giant, floating eyeballs and make Icecrown Citadel look like Barad-dur! Oh, and give him Sauron armor!”
Blizzard Executive 1: Jimmy, you’re a genius! You’ll be made board member by the time Wrath goes live!
And the rest is history.