This DLC gives you plenty of reason to return to the wonderful world of Skyrim
To activate the DLC, you have to run into this guy who will tell you about the frequent vampire attacks throughout Skyrim and that the Dawnguard, a group of vampire hunters, is being revived to take them down. After meeting Isran, their leader, and saving a vampire named Sarena, you are given the choice by her father (Lord Harkon); become a vampire and join them or leave and continue fighting for the Dawnguard. Now you must either vanquish the new vampire threat or join them and bring darkness throughout the land. Out of all the storylines in Skyrim, this may be one of the most interesting of all the guild quests.
So what is new? Well, there are new weapons to obtain. All I've noticed so far are new swords and some new armor, but the biggest addition you'll notice is the cross bow. More powerful than the long bow, the cross bow doesn't require you to hold down any button to aim and is slightly more accurate. The only downside? You need bolts instead of arrows, but you can pick them up right at the Dawnguard base. Also, a new area is unlocked along the way of the quest line. It is the Cairn where all lost souls are trapped. Thee best part about this place is you can trap souls in your soul gems easily just by walking up to them and there are more places to explore and enemies to fight. More importantly, if you finish a certain quest, you can unlock a brand new mount. Not just any mount, this fiery demon horse can be summoned anywhere (in the Cairn OR Skyrim) at any time. Adding to that, you can now wield your weapons while riding (on any horse) which was desperately needed the first time.
But let's talk about the biggest addition to this DLC pack; the vampire lord. If you decide to be bitten and gain the power, you can transform into a demonic vampire lord at any time. You lose your weapons and armor briefly but you have your own set of attacks like rising people from the dead to fight for you or simply drain their health for yours. There are more attacks to learn but only if you decide to level up and learn them from the skill tree. That's right, vampire lords (as well as werewolves as of this DLC) have their own skill trees and experience system making each of these creatures even more fun to play as. This is obviously the biggest addition and playing as one is entertaining as hell, especially attacking cities and making everyone run in fear of you.
The only problem with this DLC is the constant vampire attacks. When you enter Riften or Whiterun, the chances are good that you'll run into vampires attacking the town which makes things more problematic when they kill important characters that you need to complete quests. These happen more often than they need to and it can be frustrating to restart just in an attempt to save a guy.
I know that $20 or 1600 microsoft points may seem pricey, but Dawnguard offers just enough to live up to that asking price. With new areas to discover, a new questline that take up to 10-15 hours to complete, and new features, Dawnguard gives you plenty of reason to dust off your copy of Skyrim and play it once more. If you loved Skyrim as much as I do, do yourself a favor and purchase this DLC.