Players who choose to start a Death Knight character will begin their journey at level 55, the same level required to create one. Death Knights can be any race, but users will only be able to create one per server, according to Curse. Once created, they will begin the game with a series of specialized quests, designed to introduce the player to their new abilities.
As detailed before, Death Knights will have a two-tiered resource system. Runes slotted into their "blade" act as a basic requisite for certain spells. There will be three different types of runes, and some abilities will require a specific number of one type to be slotted before they can be used. Another resource, Runic Power, is then gained by using runic abilities during combat. The Runic Power can in turn be spent for finisher-type moves.
Death Knight abilities run the gamut from the classic Death Coil--a spell that deals 600 damage to an enemy target, or heals a friendly target for 900--to a summon ability that transforms a dead enemy into a pet ghoul, which then fights for two minutes in service of the player.
Various aura-like abilities called "Presences" will bestow the Knight with increases to armor or attack and movement speed, while a Death Grip ability will act as a powerful taunt, physically pulling enemies closer. Death Knights will also have the ability to summon a Deathcharger mount.
Speaking of mounts, the new continent of Northrend has now been approved for flight, allowing players to use their old flying mounts in the zones. Among other interesting details, the raid dungeons found on Northrend will all have 10 and 25-person versions. Higher-tiered drops will be in store for those who tackle the tougher 25-man raids.
Finally, Eurogamer reports that Arthas, the Lich King himself, will finally be open to attack with the last patch of the Lich King cycle. Players will first encounter him in the Chamber of Aspects, a dragon-populated raid zone hidden away in Northrend's Dragonblight zone. The final battle will take place in the Icecrown Citadel.
If you're looking for a comprehensive breakdown, MMO Champion is keeping track of the new details in a point-by-point list.