With End Time and Well of Eternity down, the last dungeon we examine is the Hour of Twilight. This dungeon technically takes place in the present day, acting as a precursor to the Dragon Soul raid. Unfortunately, you do have to escort Thrall through the dungeon, but if you turn off the sound on the voice acting and squint, maybe you can pretend it is a cooler shaman like Nobundo or Mylra.
For now, though, what we're most interested in is getting through this dungeon as a death knight, be that tank or DPS. It's a short, sweet dungeon, but there are a couple of tricks and gimmicks you'll want to know to make the fight as smooth as possible. As with the other two dungeons, the loot here will be mostly sidegrades to Firelands stuff, a great way to catch up an undergeared death knight for Dragon Soul. (For a more complete overview of the dungeon from all angles, be sure to check out WoW Insider's guide to Hour of Twilight.)
Trash for Arcurion, the first boss, isn't too annoying -- just some run-of-the-mill elementals. The second pack comes at you from both sides, so you may either want to wrangle the single dude in with Death Grip or have one of your DPS CC it.