Those who have purchased Elder Scrolls V: Skyrim for the XB360 are now able to buy, download, and play the first DLC titled Dawnguard. This downloadable content indroduces the VolkiharVampire Lord, Harkon. Harkon is up to no good and it is up to the Dawnguard to stop him from using the Elder Scrolls for his own personal, evil, intent. The events begin once your character starts to hear rumors, which then will lead you to Fort Dawnguard.
The Dawnguard DLC gives the player a chance to either join with Harkon or to join the Dawnguard in order to stop the Vampire Lord. Either path you choose, each has their own perks. Being part of the Dawnguard will allow your Dragonborn to gain access to new weapons (like crossbows!) and armor as well as armored trolls for hire. Working along side Harkon could allow your character to become a Vampire Lord, which entitles your character to vampiric powers.
For 1600MSP, the Dawnguard DLC can be yours on XB360. No date as of right now for those who play Skyrim on PC and Ps3 since the XB360 has exclusive rights with Bethesda.