These questions lend themselves to a spectacular conclusion to a great tale. In The Lore of Patch 3.3, Michael Sacco, Alex Ziebart, and I will take a look at all the various plots, characters, and environments that lead up to this grand confrontation with the Lich King.
You'll want to know this story. You'll want to know this lore.
For when you finally face off against the wielder of the Frostmourne, you'll know why you're going toe-to-toe against him, and why your fate can make or break the very face of Azeroth.
This article, while containing essential lore, also contains heavy spoilers. Do not proceed if that bothers you.