Just saw the latest Legend of Korra episode (the one with the flashback to the first avatar). Awesome ep! Pretty much lead me to believe Unalaq is going to be the one to free Vaatu, and become the first "Dark Avatar" to take on Korra and Raava. I'm probably completely wrong, but felt like drawing what i pictured unalaq and vaatu joining forces would look like.
This is a WIP progress. Started laying down the rough sketch lines, but wanted to convey the glowing tattoos that were similar to the spirit Vaatu, so started laying down some rough colors.