If you were excited about Dawnguard, Skyrim's first piece of DLC, before, wait until you see it in action. The video shows you the vampire lord transformation and the skills that come with it, including summoning a gargoyle, using "vampiric grip" to lift enemies in the air, melee attacks and shooting energy balls. It also shows a bit of the Vampire Lord perk tree.
The video also shows off how crossbows work and a bit of the mounted combat.
Part two of the video confirms new shouts for the DLC. Watch it here: