In one corner, we have Sauron: The Dark Lord with an army of hundreds of thousands of Evil creatures and the Nazgul under his command.
And in the other, we have A Song of Ice and Fire's greatest and most feared being. He is secretly a Targaryen, and the prophesied The Prince That Was Promised--essentially a Jesus that would destroy the White Walkers and bring order and stability to the world.
Spoiler
Mother.
Fucking. HODOR.