Skyrim's first expansion pack Dawnguard won't let players play as a Vampire and a Werewolf at the same time, VideoGamer can reveal.

Dawnguard, which launched on Xbox Live Marketplace this morning, makes players choose between joining the vampire hunting Dawnguard faction or becoming a Vampire Lord themselves. Bethesda says the expansion adds 20 hours of content to the main game.

However, characters suffering a spot of lycanthropy will have no choice but to surrender their bestial abilities if they want to go the way of the nosferatu - Skyrim won't let you have both active at once.

Players are forced to become a werewolf during Skyrim's Companion quests. It is currently unknown what happens if you attempt this quest-line after having already become a Vampire Lord.

Unlike the werewolf form, which can only be triggered once every 24 hours, assuming your Vampire Lord abilities does not cause NPCs to attack you on sight, though you will find yourself occasionally hunted by the Dawnguard.

Skyrim's Dawnguard-only Vampire Lord abilities are different to the vampirism that develops after catching the Sanguinare Vampiris disease in the main game - though you're immune to that if you happen to be a Werewolf, coincidentally.

If you've bought Dawnguard and are wondering how to access the new content, make sure to check out Bethesda's official guide.