How can I win this game?

Hint 1 of 11:

The Yus aren't very observant.

Hint 2 of 11:

You can basically do anything you want to to the ball, and they won't notice.

Hint 3 of 11:

Have you found a spell that might act on the volleyball?

Hint 4 of 11:

You will need to make a withdrawal first.

Hint 5 of 11:

From the bank in the mining town, that is.

Hint 6 of 11:

The rummy in the groggery will help you get into the safety deposit box.  See
the question in the "Other Puzzles" section for more information.

Hint 7 of 11:

It's very hard to hit a flat ball.