In the world of Valanas, Aether permeates everything. It is the fabric to which everything is sewn and the breath to which all things are given life and sentience.
Sansin Cain, Immortal Aether Sage is a man who has mastered the use of Aether, and as such has become one of the most well known manipulators of Aether... as well as the most controversial.
Aether is a magical element found within the world can be manipulated and enhanced by many, either through how many threads are connected to any given source or by how this source focuses the connections of aether through the use of runes, kisetsu, or by use of various materials in the world such as Mithril.
Sansin Cain was one of those Terrans who had invested so much passion into it, because it was by far the most interesting things that seemed to have so little known about it. At a very young age, Cain had mastered the use of Kisetsu, which at the time was simply a technique to allow someone to meditate and gain focus.
Cain didn't want to settle with just that, using the art of Kisetsu, he was one of the first who was able to utilize Kisetsu in order to subtly manipulate the world around him. By the time he had come of age to become a prince, Kisetsu gave up his royalty for the sake of pursuing his study of the use of mithril with Kisetsu.
With the combination of these efforts, he had been able to understand the basic principles of Aether manipulation, allowing him to manifest potent abilities that pushed the very Laws of Creation that many had thought before to have been impossible to break.
From this point on, Cain quickly gained the title as Sansin, having helped defend the Terran nation from various invasions, though many people do not realize that the efforts were simply him "experimenting."
When it came time to hunt down and face Atlas, Cain found the opponent to be a worthy challenge. Cain's mastery of Magic and Atlas' potent bloodline ability proved to be one of the very few elements that allowed for the defeat of the Naganezu.
Though during that fateful day, something drastically changed in Cain. His mastery moved to such a degree that his very body seemed to have been infused with Aether and Mithril, causing his body to become substantially unstable. Due to his training, he was able to control it to a point that it changed his body completely, though many people are not fully aware to what extent.
Instead, now Cain has began to focus his research on how to awaken the bloodlines of all the living things across Valanas, regardless of the consequences it may cause. It is his firm belief that in order to prevent the same thing that has happened in the past, people need to not be limited by "petty laws" and instead should have the absolute freedom to make the choice for themselves.
Though, as many would learn, that isn't always something people have wanted to experience, and in the case of Katara, is something so delightfully delicious... that his intentions can often times cause more harm than good.