A swapling is a lowfolk child stolen by elves, who leave their own baby in its place as a "changeling."

The fate of swaplings is varied and mysterious. In the middle Imperial period they were kept as indentured servants until their corresponding changeling returned to Faerie, at which point they were given the choice to remain in Faerie or return to the lowfolk world. According to the stories, most chose to stay. Unseelie elves of the Long Ago were rumored to have sacrificed or eaten swaplings, both of which practices are illegal in the Mephitist Empire. However, during the reign of King Gawain Adlersson swaplings were killed so that their spiritual essence could be harvested and merged with changelings as they passed through the Ferifax Arch. This process produced a hybrid creature known as a "crossling."