Once you have reached cap level, you will be assigned a warplot on a floating island. It will be up to you to build it up into a battlefield. Items for your warplot can be gained through raids and adventuring. Defeated raid bosses can be added to your warplot but will be a significantly weaker version of their former selves. Once your warplot is ready for battle, you can initiate a war via a matchmaking system. Group sizes are 20 man and 40 man. Once two warplots have been chosen, they will be instanced within range of eachother and the battle will begin. If you lose and your warplot is destroyed, you will have to buy a new piece of land and rebuild. Winners will gain rewards based on their victory.
Warplot Plugs
Media
Source
http://www.youtube.com/watch?feature=player_embedded&v=dDfQEhnHFak