Creates an Acorn Whistle that you can trade or mail to another player, which allows them to summon you to them. You must be together in a fellowship for them to be able to use it, and you will receive a confirmation box to accept the summon.
The whistle will disappear after one use. Individuals can only have one whistle per guardian in their inventory, including the guardian themselves.
Since the update that allows VIP players to access their mailbox anywhere, this is now an extremely useful porting device to get a guardian anywhere in Middle Earth.