Beta testers on Skyrim’s Dawnguard expansion have begun detailing the add-on’s content.

The story focuses on a vampire lord called Harkon who is intent on using an Elder Scroll to blot out the sun. You’ll have the choice of either joining Harkon’s gang or the Dawnguard, a group of vampire slayers.

If you join Harkon you’ll be able to become a vampire lord. The process works in much the same fashion as being a werewolf and unlocks an ability called Vampiric Grip that drains the health of enemies while suspending them in the air. You’ll also be able to turn into a cloud of bats.

There’s downsides, however. Being a vampire means that NPC’s will attack you on site so you’ll have to change into your human form.

Meanwhile, joining the Dawnguard offers you access to new weapons, including the crossbow. They’re slow to download but are always primed to fire and can stagger targets. As a Dawnguard you can also hire armored trolls as followers.

In addition to all this, the add-on brings a new Dragon Shout. It’s called Soul Tear and allows you to steal a victim’s soul and then raise them from the dead as your companion. Also, there's a summon anywhere skeleton horse.

Check out the full vampire and new werewolf perk trees below.

Vampire Perks 

• Power of the Grave - 50 point bonus to health, magicka and stamina as a Vampire Lord
• Detect All Creatures (requires Power of the Grave)
• Mist Form - turn yourself into an invulnerable cloud of mist while regenerating your health, magicka, and stamina (requires Detect All Creatures)
• Supernatural Reflexes - you move quicker, enemies move slower (requires Mist Form)
• Blood Healing - killing a person with a power attack bite restores all your health. (requires Power of the Grave)
• Unearthly Will - night powers and Blood Magic cost 33% less (requires Power of the Grave)
• Poison Talons - melee attacks deal 20 points of poison damage (requires Unearthly Will and Blood Healing)
• Night Cloak - a shroud of bats feed on enemies within melee range. (requires Poison Talons)
• Vampiric Grip - Blood Magic: can pull a creature to you from a distance, and do choking damage once it's close (requires Power of the Grave)
• Summon Gargoyle (requires Vampiric Grip)
• Corpse Curse - paralyze your foes with this magical blast (requires Summon Gargoyle)

Werewolf Perks

• Bestial Strength (four levels) - first level: do 25% more damage as a werewolf
• Totem of Ice Brothers (requires Bestial Strength)
• Totem of the Predator (requires Bestial Strength)
• Totem of Terror - Werewolf Howl of Terror affects even higher level creatures (requires Bestial Strength)
• Totem of the Moon - summon an ally werewolf with a howl. (requires Totem of Ice Brothers)
• Animal Vigor - 100 point bonus to health and stamina in beast form. (requires Bestial Strength)
• Gorging - feeding heals twice as much health (requires Animal Vigor)
• Savage Feeding - (requires Gorging) 

[via OPM]