Whump idea of the day:
Magical restraints - that is, shackles locked not with a key, but with magic. Forged from the strongest of materials, charmed to be unbreakable by brute force. A spell is the only way to remove them.
A captive being rescued by someone unable to use magic. They can be carried to safety, but their shackles remain locked. They must remain in chains even after rescue, until someone with magic can free them. Still limited in motion, still dependent, still not quite free.
Or worse, the rescue failing, because the chains are connected to something - the wall, the floor, a weight. The rescuers swearing they'll come back, that they'll find someone with magic who can help. Trying to comfort the captive as best they can, but ultimately forced to leave them alone - or else risk their own capture.
Or maybe, the captor is the only one who can use the spell to unlock the restraints. The captive - or their rescuers - having no choice but to bargain for their freedom.