How to Create a God in a World of Unbelieving People?

Gaius Juin is the land Ace wanted to go. They said, it's the only place in the Sphere that the Sun can be seen.
He never saw the sun, in fact, nobody in their land saw the sun.

The giant walls surrounding their land prevented Ace to look at it. In fact, it prevented them to go beyond other lands because they said, it would cost them their life. But by a twist of fate, Ace was sacrificed to the walls and delivered to the other land as an offering.