Northrend will feature, on all realms both PvP and PvE, a zone that will flag everyone who enters PvP. This zone is in the center of the new land, allowing people who don't want the PvP hassle to easily go around it while those who dream of ganking undead warlocks can have a field day.

The PvP zone is called Lake Winterspring, and while by far the biggest innovation to PvP announced in the upcoming expansion, it is not the only one. There will be new battlegrounds and arena season.  Blizzard is expecting the new battlegrounds to field 15 players on each side, complete with siege engines and destructible buildings.

For the first time in its history, World of Warcraft will introduce a hero class: the Death Knight. The Death Knight will be available through a quest line players can unlock once they reach level 80. At the end of the quest line, a new character is available to play. The Death Knight is a plate wearing, two-hand sword or duel-wielding madman who can both tank and DPS. The Death Knight will enter the game at a high level - the exact level is yet to be determined, but 55, 60 and 65 were all mentioned - and your original toon will still be the class and level they were. It should be noted that the Death Knight will not replace the original character.

Death Knights are oriented around runes and runic weapons. Depending on which spell or ability you want to use, they can inscribe different runes onto their blades (runes come from three families, Blood, Frost and Unholy). These runes can be drained of their power, and must be recharged to use again.  A Death Knight player will see another bar under his health bar - where rage/energy/mana usually is - that shows which runes he has and if they are charged or not.

Blizzard plans on introducing other hero classes into the game after the expansion is released, and warned the fans at BlizzCon to expect to start seeing all the heroes from Warcraft 3.

To the shouted question from the back of the hall asking when can we expect to see it, the Blizzard developers replied "When it's ready." While you're waiting for Blizzard to ready announcements on future hero classes, give the Images tab above a poke for a early look at some of the new areas you'll see in Wrath of the Lich King.