So over the course of the next 4-5 months they'll be dropping in expansion level content to the game. It'll feature live events, 2 new classes and a new area for the realms to fight for control of.
I like the format of the event. It feels like it is adding a timeline and history to the game, rather than simply dropping a brick of new stuff on the game and saying 'have at it'
As with the Black Guard and Knight of the Blazing Sun, the new Choppa and Slayer will be unlockable 1 week early by folks who participate in daily events.
Here's the official link
EDIT: BAH! Beat by 2 minutes!