Picture by Danboruu
Lumine and Aether were traveling between worlds when they ran into an unknown god. The unknown god seperated the two twins after they tried to fight back. You can choose to be either Aether or Lumine. After they get seperated the twin that you choose has to complete grueling tasks to recieve help to find their twin. They get more and more irritated because they have to keep doing stuff for people that won't help them. When they see each other, you find out that the twin you didn't choose becomes the Abyss Prince/Princess which is the main villain in the story. The twin you didn't choose is the one who began the abyss order.
The two characters are nice and patient. They do tasks for people to get help, but they don't refuse or get angry when it doesn't benefit them. We even get to see that when the traveller unlocks their first Statue of the Seven because it says it opens itself to those with Noble hearts. But lately into the game the traveller's have been getting a lot more frustrated because people have been taking advatage of them way too much and all the traveller wants to do is find their missing twin.
After the twin you chose defeats Stormterror and Venti purifies him, the traveller gets to complete after quests for other characters. This earns you the trust and friendship of Jean, Lisa, Kaeya, Diluc, and Venti.
The traveller's only goal is to find their twin, but they keep getting side tracked with other misions. So while looking for their twin they have to protect the nations and overcome some huge quest in order to move on.
The travellers aren't from Teyvat so they don't have visions but they are granted the ability to use visions from the Seven. Right now, they are able to use Electro, Anemo, and Geo. They are not able to use the other visions yet since the developers haven't put out the other nations ruled by the Seven.
They're my favorite genshin character because of how over powered they are. I love that they also do tasks for other citizens in exchange for help or tips to find their twin which they never get.