Demon Contract

An assassin infiltrates an auction to kill her target, but fails when she discovers he is a demon. He takes her to his lair. She escapes during her heat cycle, traps him with vines, and returns to her elven home—but he follows, and they share an intense encounter. She orders him to leave by day's end, then patrols with a fellow elf who notices marks on her neck. The demon, disguised as a human merchant, uses valuable resources to win over the elves and moves in with her. He takes a wound meant for her during a patrol, using it as an excuse for closeness. She notices he knows her too well and suspects her memories have been tampered with. The suspicious elder sends her on a dangerous mission; the demon follows and reveals his true power. The elder exposes him publicly; she is forced to wound him to avoid arrest. He is imprisoned. She rescues him, finds the elder summoning forbidden power, they destroy the elder together, calm his rage, and leave the tribe behind.