Here's the intro video, in case you want to see it now.
The Death Knight starts at Acherus, a Necropolis located near Hope's Light Chapel. Right in front of you is Arthas, the Lich King. He gives you your first quest, which sends you on a path to learn Runeforging and defeat an initiate.
Runeforging is kind of like a tradeskill but kind of not. The Death Knight learns a bunch of enchants that cost no reagents and only apply to their weapons. The main contingency is that you can only use this "tradeskill" when you are near a runeforge. These enchants are wicked awesome. From what I've seen, I imagine at high levels you will not be using an enchanter to buff up your weapons. Here are some examples...
These are the ones that I had by level 59.
After you gain your Runeforging ability and deal with a short quest where you fight another Death Knight, you are sent down to the surface to join in on the assault against the Scarlet. You're first quest when you get down there is to win five duels. They've actually put NPCs in this area that you can challenge to duels much like you would a player.
Once you finish dueling, you are sent out to steal a horse that becomes your "Acherus Deathcharger", an epic mount unique to the Death Knight.
You go on a quest to kill something like 115 Scarlet soldiers. To do this, you have to get on this boat and man a cannon that fires cannon balls and giant explosions. At this point, I still hadn't done what I would call a "traditional" WoW quest. Something of note, you start out with 0 talent points when you create a Death Knight. As you quest in this area, you are awarded 1-3 talent points for just about every quest.
There was a quest where you had to kill a bunch of civilians with this device that would turn them into ghouls. During this, the Lich King would occasionally whisper to you things like "Kill them all" "You are an abomination". Very freaky.
Something else I want to mention is that the Death Knight section introduces Instanced questing. The Death Knight starting area seems to exist in different phases. Whenever you complete certain quests, you are taking to a new instance of the area. This creates an experience that makes it feel like you are personally changing the outcome of what happens in this area. Truly amazing.
I've only talked about the first half of the Death Knight quests. The last half and the super epic finale will come later. What I'm going to talk about now is EXACTLY how the Death Knight works.
So if you know much about Death Knights, you know that they are suppose to be able to tank without a shield. How does that work? For one, they get a huge amount of Hit Points at base. All Death Knights also get a passive ability called "Forceful Deflection" that increases your parry rating by 25% of your strength. Something that most people don't know, but whenever you parry, the time left for the next swing of your weapon is cut in half. This is pretty amazing.
Another important mechanic to the Death Knight are their "Presence" stances.
Blood Presence is a powerful damage dealing stance that increases all damage dealt by 15% and the Death Knight is healed for 2% of all damage that they deal. Unholy Presence is another powerful damage dealing stance that increases their attack speed by 15% and reduces the global cooldown on all of their abilities by 0.5 seconds. Then there's Frost Presence. This monstrous stance is for tanking, increasing their armor contribution from their equipment by 25%, their threat generated by 45%, and all magic resistances by 30. The magic resistance granted by this presence might increase based on your level, but I'm not certain.
Every talent tree for the Death Knight includes some tanking abilities. What's extraordinary about the Death Knight is that each talent tree includes SIX new abilities and you can easily spec into another tree to have seven abilities granted by your talents by the time you reach level 80.
You should also know that Death Knights don't get ranged weapons. They get Sigils, much like a Shaman's totem or a Paladin's Libram.
Now you kind of now how they are able to tank, but what about the whole Runic Power & Rune system? I'll tell you all about it. The Rune system is extremely different from mana, energy, rage, or combo points. Each Rune represent either Blood, Frost, or Unholy. Many of the Death Knights abilities cost a Rune or two. When a Rune is spent, it goes into a 12 second cooldown. You get two of each rune, so spending one Frost rune still means that you could immediately spend another. There are also special talents that convert certain types of Runes into "Death" runes, which count as Blood, Frost, AND Unholy runes. Once a Death Rune is spent, the rune converts back to what it was originally.
Runic Power works much like rage but has a few special contingencies. When you use an ability that costs a rune, you generate some Runic Power. This is the only way to gain Runic Power. You don't gain any from getting hit or dealing damage (usually). When you spend a rune, you gain a significant amount of Runic Power, usually enough to at least use a couple of your abilities that cost Runic Power. Runic Power also drains very slowly out of combat, so you generally retain most of your Runic Power between fights if you are actively grinding.
Based upon my experience with the Death Knight, it will be my new main character when the expansion hits. I have so much fun playing as one that I've actually gone to the outlands in the Beta, which I feel kind of stupid about considering I've seen all of that place before. I can't help it. They're just too much fun.