The Forestbenders use their powers to give Khan some of their magic, and he becomes a Forestbender. And of course there is a hot girl that helps Khan become a better person through love. The leader tells Khan that this is a new continent, and only the Avatars can find it. The leader of the Forestbenders explains Khan that the world is now very different, because now there are new races and benders out there. Khan learns that Korra action all these years ago in the Harmonic Convergence cussed a shift in the world, and this is also why there are 2 Avatars now.
Vin can’t stop them alone, and so he goes to find Khan, hoping that his brother can help him.
After many surgeries, all the member of the group can now control all 4 elements, and now they go to take over the world, but only 5 of them survive the surgeries. Most of the test subjects die, but then Zane goes through the presider, and he learns that now he can control 2 different elements. In their first battle, Vin is able to defeat Zane, and this makes Zane to order the scientist to start testing on benders, trying to give a bender more than one element. Zane wants to turn more people into benders, he also hates Vin for what he has done to Khan (taking his bending away). Zane’s group believes that non-benders should be their slaves, because they are sub-humans. They both started a group of benders that believe in a new world order. Zane is a Firebender, he and Khan became like brothers years ago, when Khan was getting his Firebending training. It is revealed that Dr.Yan is working for a group of benders, who are led by Zane, and he shares Khan’s ideology about benders and non-benders. Non-benders start paying for this surgery and they become benders, and that creates a whole new chaos, because now everyone is a bender. With a surgery, Dr.Yan can give any man the powers of one of the elements. Yan, shocks the world when he reveals that he can turn any non-bender into a bender (for the right price of course). The world is different, and is a mixture of present and ancient times (like it was in Korra, a mix between different eras). Korra died when she was in her 60’s, and the two brothers are in their late teens, so it’s been almost 60 years since the events of “Korra”. The story of the show picks up after the two brothers already mastered all the bending skills, and they are both very powerful benders and Avatars. He believes that the world’s Kings and leaders are not needed, and he is the one that needs to rule, not because he wants the power, but because he is the Avatar, and he is the bridge between all nations and benders. He thinks that being an Avatar means that he has to save the world from evil and injustice, and he is ready to do the wrong things to achieve his goal. Khan on the other hand is much more aggressive in his beliefs. Vin believes in good and always tries to do the good thing, he believes that being an Avatar means he has to keep the peace and the balance in the world. Their relationship is little similar to Professor X and Magneto/Thor and Loki. I know that these two brothers might be little similar to Mako and Bolin from “Korra”, but there are very different.