The video hints at the new plotline and confirms the inclusion of crossbows as a weapon.
'Dawnguard' will be available on Xbox 360 this summer as a timed exclusive for 30 days, and will be available to download for 1600 Microsoft Points (£15 / $20).
Earlier this month, Bethesda released an update for the Xbox 360 version of Skyrim that adds Kinect support for over 200 voice commands. Commands include telling the game to save, commanding followers and using dragon shouts.
The Elder Scrolls V: Skyrim was released for PC, PlayStation 3 and Xbox 360 in November. It was named as the fastest-selling PC game on digital distribution service Steam.
Full details on the 'Dawnguard' DLC will be announced at E3 2012 in June.
The E3 Expo will take place in Los Angeles from June 4 to June 7.
> E3 2012: Digital Spy's coverage from the world's biggest gaming expo
> Read our review of Elder Scrolls V: Skyrim
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Copyright: Bethesda Softworks