Maddox Fisk is one of Grandpa's friends, brother of Dougan Fisk, and works as a fairy broker, among other things, which means that he catches and sells or trades fairies. He is taller than Stan Sorenson and has much broader, withcurly brown hair. The layers of furry skins he wears make him look like a mountain man. He is missing the bottom of one earlobe. He presents to the Sorensons his collection of fairies that he had gathered from around the world. His most prized one is a Jinn Harp, of which there was thought to have only been one in the world.
Book I: Fablehaven
He trades various fairies with Stan Sorenson.
In book 3, it is mentioned that Maddox went on a mission to a fallen preserve in Brazil and has not been heard from since. Tanu went to search for him, but did not succeed in finding him. Tanu did, however, leave a tub behind that exists in the same time and space as an identical tub in the attic in Fablehaven.
In book 5, Maddox is found in the dungeon of the Living Mirage preserve.