Guild Wars 2 world vs. world battles consist of three entire servers fighting against each other in battles that last two weeks, and rage on maps that support more than 300 players.
And anyone can play: characters are automatically adjusted to be "roughly equivalent" to a top-level, level-80 character.
If you win, your server ranking improves, and you'll be matched against server-opponents accordingly.
Systems designer Mike Ferguson explained world versus world battles on the ArenaNet blog.
Battles span four maps in an area called The Mists: three home maps called Borderlands - where each team has a home advantage - and one central map called the Eternal Battleground.
Each map has keeps, towers and resource camps, which create the universal resource called "supply". Capturing any of these improves your team/server's War Score.
Keeps are hardest to take. They've got tough NPC defenders, walls, gates and a boss lord. That's without human-controlled defenders.
You'll need a full complement of siege weaponry to break a keep: the options are Trebuchet, Arrow Carts (projectile launchers), Catapults, Ballistae and Siege Golems (a slow, robotic juggernaut). Building siege weapons requires "supply", which players can deliver. If you're defending, "supply" comes from caravans, which will need protecting.
Guilds can claim keeps and upgrade them. ArenaNet says a winning team will be one that breaks off into guilds and tries to obtain multiple objectives at once. The keep's structure can be upgraded by paying gold and then waiting for worker NPCs to do their thing. The keep's guards can be upgraded too, by paying gold.
You'll also fight over Orbs of Power, which are hidden in a special Cradle of Power keep at the heart of each team/server's Borderlands map. This will be guarded by a boss called the Keeper. But steal an Orb of Power and stuff it on an Alter of Power (available at any keep) and the abilities of all of your team/server's characters will be boosted.
While level 1 characters will be boosted to level 80, they'll not be as powerful as someone who's naturally risen through the ranks. A natural level 80 will have "a clear advantage", although the fight won't be over in one hit.
"So what's a low-level character to do? Anybody can man a siege weapon, help repair walls, or go hunt down enemy dolyaks, so even new characters can still be useful in the Mists - as long as they pick their fights wisely," explained Ferguson.
"Fights are rarely one-on-one affairs, so if you're just starting out, you'd be wise to find some teammates to fight alongside you as there definitely is strength in numbers."
You'll gain experience and new items during world versus world battles as well. Killed enemy players drop loot, but you won't lose any of your own if you die. All dropped loot will be level appropriate.
You can even convince NPC mercenaries and monsters to fight for your cause, such as ogres, stomp stomp stomp.
The Guild Wars 2 open beta begins in March.