What can I do with Othello?

Hint 1 of 9:

He might like something in your inventory.

Hint 2 of 9:

Something valuable.

Hint 3 of 9:

Try giving him the coin.  You'll get a key in exchange.

Hint 4 of 9:

The key opens a door very close by.

Hint 5 of 9:

It's the door just below his cage.  Use the key on the door to unlock it.

Hint 6 of 9:

The problem, though, is figuring out how to get through that door.

Hint 7 of 9:

You need to find something small enough to go in there.