You stumble onto the conflict between the vampires and the Dawnguard by chatting to the guards of Skyrim, who don't waste any time in informing you the Dawnguard are recruiting once you've purchased and installed the first expansion pack for The Elder Scrolls V: Skyrim.

An E3 2012 demo of the game takes place between three and five hours into the new content, which is promised to be over twenty hours long - though a Bethesda representative wouldn't confirm if that figure was calculated after playing the content once as each faction. You've got to choose between becoming a vampire lord or serving in the Dawnguard, you see, and almost everyone I know has pledged to walk the path of the Nosferatu.

The demo had me playing as a vampire (it's as if they knew) and thrown into a quest with a character called Serana, also a vampire, searching for her mother by opening a portal to the Soul Cairn - a new dimension of Oblivion that's terrifyingly purple. Serana's quest is tied to the location of an Elder Scroll, but I didn't get to play much farther than a couple of quests so you don't need to worry about spoilers.

Becoming a Vampire Lord makes you weaker during the day but also gives you the ability to transform in a way similar to the werewolf from the main game, only with the option to turn back whenever you want. A Vampire Lord can choose to either walk or float, and attacks with melee when their feet are on the ground and magic in the air - you toggle between the two states by pressing the sneak button.

Then there's your abilities. First off, the fun ones: Vampire Grip is the stand out highlight, which sucks enemies towards you and has you drain them of life and fling them aside afterwards. You can also teleport into a swarm of bats and hop around the map, summon gargoyles and paralyse foes with corpse curse.

Elsewhere there's stuff like Power of the Grave, which gives you stat bonuses across the board, a boost to your reflexes, an ability to detect all creatures and a whizzy mist form. I didn't get to try all of these out - they're all part of a two-branch perk tree that you unlock once you choose the vampiric side, and if you elect to go for the goody two-shoes Dawnguard lot you'll unlock another skill tree. The vampire hunters get access to crossbows, loads of armour and can summon the assistance of trolls. No, I have no idea how.

You faction choice (and whizzy new powers) carry over into the rest of the game, so the real highlight of Dawnguard at this stage appears to be in further tailoring your precious Skyrim character. Be warned, however, as there's no way to go back and pick the other side without starting a fresh character.

As for the quest on offer in this preview build, it had the player locate and rummage around three massive spires to destroy their keepers, which felt like pretty standard Skyrim stuff. Only now you're a vampire, and that's great.

The 1600 Microsoft Point asking price for Dawnguard certainly looks a bit steep, but if Bethesda isn't telling porkies with the amount of content you're getting it could be a real highlight this summer.

I'm definitely siding with the vampires.

The Elder Scrolls V: Dawnguard is released exclusively on Xbox 360 on June 26. PC and PS3 versions of the add-on will arrive a minimum of 30 days later.