There isn't anything left to do here. Where should I go next?

Hint 1 of 12:

First, make sure that you've found all four elements in the temple.

Hint 2 of 12:

Once you do that, you'll be given a gift by the alchemists.

Hint 3 of 12:

It's a bright ball.

Hint 4 of 12:

Have you seen any places that could use such a ball?

Hint 5 of 12:

One that looks like a sun?

Hint 6 of 12:

Go to the model of the solar system in the dome behind the altar, and you
should notice that it's missing a sun.

Hint 7 of 12:

The left-hand set of controls allow you to put the sun into the model.