Venti was FGoD Error, ever since Error fell into the void he got turned into a wind whisp in Tevyat, the story goes the same being the wind wisp find himself a friend, war broke out and all that jazz and Error is happy and enjoying with his new life and job as Venti and The God of Freedom, but knowing that his multiverse that still alive is now happy and stable ( He knows this because his soul is still connected to his home ) He really just want to go back and hug his family but unable too because he can't travel between universes ( I assume that the universe is different fandoms ( correct me if I'm wrong )) and he still wants to look over his city until traveler came, finding out that he can travel throughout universes but unable too right now because of a seal, he decided to help the traveler so the traveler can help him visit his home

There is a few of reason why I think this is possible so welp, Ima list them down:
- FGoD Error can play any string base instrument 
- He would definitely help Mondstadt to gain their freedom 'cause he knows how it feels to be trap
- Some FGoD Error doesn't have a good childhood at all so knowing that they're free they would act childish and sly ( like someone we know- )