The King's Wit is a Jester of sorts in the Stormlight Archive series. His name is Hoid, and he appears as a character in many of Brandon Sanderson's works, though not always in such a large role.
With this card's ability to travel between worlds, you can pick up your favorite card and keep it to yourself for the next round.
Aside from being a Light Unit who can be used to help create any Village, the King's Wit is useful for keeping a valuable (like a King) or powerful (like a Dragon) unit. If you don't have anything useful, you can always keep the King's Wit so that making a new Village the next round will be easier.