Along with this image Bryan said
"Mixing some Book 2. Adrian on the board. Mike is my copilot."
As far as I know mixing refers to audio mixing, which would be one of the last stages of production. Things are getting much closer.
The big thing here though would be that we see that the new character we thought was named Verrick is according to Bryan's tumblr tags named Varrick. Nice to get his name confirmed. Really makes me wonder why they don't just show the names written down on the slides, the amount of names that get confused is insane.
What we know about Varrick so far is that he is a Captain of Industry from the Southern Water Tribe and is quite flamboyant, also that he has an odd friendship with Bolin. Interesting here in that both Korra and Varrick are from the Southern tribe so perhaps they know each other.
Thoughts ?
