The first Dragon Age II downloadable content is just downright great. I'll try and sell it in a few hundred words, but if you trust me then just go download it right now.
Here's the story: a mysterious clan is hunting the Hawke family for their blood. Why? Well, that's what you need to find out. To do it, you'll travel to a new location, fight your way through hordes of bloodthirsty dwarves and their pets, then delve back into the heart of the Blight: the Darkroads. There, you'll meet a strange (and downright interesting/funny/weird) Warden knight who tells you of a mysterious Darkspawn who can think and speak, who's been locked up at the behest of the wardens.
As you travel deeper into the massive level, you can piece together clues from old diary notes of those who have traveled before you. Add onto this the fact that your party members converse (and thus don't seem quite so "tacked on" like other downoadable content) and the fact that you'll be piecing together a great story that provides a history of the Hawke family, and you have a fantastic story.
On top of that, you'll encounter a few new enemies that will provide a great fight. Expect not just Darkspawn but wardens as well, and who you fight will depend entirely on the decisions you make. That's rightin addition to the great story, you'll get to make a few crucial choices, too, which only adds to all the fun that's going on.
This is what downloadable content is all about. It's worth the $10 and, although the ending gets a little strange, the boss battle is a respectable challenge that'll make you sweat bullets. Save often. Have fun.