A crossling is a changeling infused with the spiritual essence of a murdered lowfolk swapling. This process takes place when the changeling passes through the Ferifax Arch. Crosslings were supposed to be elves imbued with the vigor and physical vitality of the lowfolk - but it was discovered that they had virtually no magickal power, had drastically shortened lifespans & decreased intelligence, and were not blessed by Fuma with the increase in fertility that had been expected.
Certain dissident groups such as F.E.L.F. and the Sisterhood considered crosslings to be an abomination and an affront to elvish dignity. The crossling project was halted when the Ferifax Arch was blown up by persons unknown in an act of treasonous sabotage.