Guard Stan:
Oh, you picked a Silver Undine. Now how should we trade? You can trade 1 Silver undine for 5 Silver Golem and 5 Silver Fairies. Or, you can play the game that is popular among collectors and obtain it at a better bargain.
Trade it at the standard rate.
Play the game [Get it correct on the second try - 3 Silver Fairies]
Play the game [Get it correct on the third try - 7 Silver Fairies]
Play the game [Get it correct on the fourth try - 9 Silver Fairies]
Listen to the game instructions.