HBO has released a very brief teaser trailer for the fifth season of Game of Thrones. It seems to put the focus on the character Arya Stark. It features her waking from dreams or visions of her killing Rorge and handing over the Faceless Man's coin to book passage at the end of Season 4. We get a glimpse of her father’s sword, which is now melted down, and that's followed by a shot of some doors. Perhaps this is the entrance to the House of Black and White?
In addition to the video, a new viral site called ThreeEyedRaven.com has launched, which allows you to sign up for "visions of the future." I imagine that we'll see a few more teasers released in the near future.