|"I have failed you, Vaatu."|
|— Unalaq when he believes that there is no way of freeing Vaatu.|
It really is not known how long Unalaq had secretly been working with Vaatu. Unalaq supposedly learned about Vaatu, Raava and Wan along with Zaheer when they joined the Red Lotus as teenagers. At some point, Unalaq drifted away from the Red Lotus and formed his own plans with Vaatu. I'm not sure exactly when the Unavaatu ship first set sail but I'm betting that it happened around the time when Unalaq revealed his desire to become the Dark Avatar, which everybody was already expecting anyway. I saw some confusion over this and yes, while Unavaatu refers to the Dark Avatar (at least in its giant form), it is also used to refer to the ship between Unalaq and Vaatu.
I don't really ship Unavaatu just like how I don't ship Waava. There is the fact that Unalaq was already married to a woman named Malina, though we do not know if their marriage was happy. They were probably still married at least since Desna and Eska were worried about how they were going to tell their mother about Unalaq's death. Granted, I do kind of see Unavaatu in a similar manner to Zhaozai where the two might be too evil for anybody else but each other. However, just like Raava, I do not see Vaatu as a sexual being or being romantially or sexually attracted to anybody.
- They work well together and are loyal to each other.
- It is unknown if they were even attracted to each other.
- Unalaq was already married to Malina.
- Both are now dead with Vaatu being stuck inside of Raava for another 10,000 years.