Book 2: Spirits is the second season of The Legend of Korra, and there has been many speculations and theories about it. The creators said that it will be much darker than Book 1 and that it will have no shortage of spirits, so we have a point there. But this blog is mainly speculating on the Spirit World in Book 2.
Many theories have been made about this image right here
As you see, that is a Spirit World strait from a Studio Ghibli film. Some theories indicate that the figure in the left is Noatak ( Amon ) and the figure on the right is Tarrlok. This theory has been made that we will probably see them in the Spirit World as (obiously) spirits. There also seems to be a path of some type leading to somewhere.
The Dark Spirit is the main villian for Book 2, and will be voiced by Grey DeLise, the same voice actor for Azula back in the original series, which gives a clue for it. I think that The Dark Spirit is Azula's spirit, trapped in an eternal prison inside TDS (The Dark Spirit) and will try to dominate the world like her father did before her. It has also been said that this Book will also include more details on the first Avatar, which is pretty interesting. Two episodes in the Book will be dedicated to the Spirit World, which I'm excited about, since we will see familiar spirits like Koh and Hei Bai. ( Maybe the Monkey Spirit from ATLA? )
Theories have been made for this image here.
They say that this is the Iceberg Aang emerged from at the start of ATLA. But let me get this strait, this IS NOT Aang's Iceberg! If you remember at the first episode of Avatar, Aang's Iceberg was in the ocean, and not in that tundra-like landmass you see there. It is concept art, but it could still be included into the series.
Well, this blog post has gotten long enough, maybe I'll do a second part where I explain the characters.
Hope you enjoyed my post and comment your opinions and feel free to like :)