The swamp hag is found in the bogs and swamps of Fablehaven. Swamp hags sometimes create false paths to lure travelers toward them. A swamp hag is mentioned to have trained Muriel Taggert in dark magic. In Grip of the Shadow Plague, she is suspected to be the one that created the shadow plague, but Grandma Sorenson said she would not have enough power. The swamp hag is the opposite of a nymph according to Newel. She lives in the Great Marsh.