Plarium says they're giving us a new champion, as a reward if we finish Faction Wars.

"While we cannot reveal the exact details, this Champion is definitely going to be a powerful one, and she will be a worthy reward to all those who manage to accomplish a feat of that immense difficulty. "

She certainly LOOKS powerful:

Wait, no, wrong pic. That's Kerrigan from Starcraft. THIS is the new Raid champ:

Can't imagine how I confused them.

Well, at least she's hot.