This comes from the fantasy series
The Witcher, which I can rarely make head nor tail of, so little am I committed to the details of the imagined world. That doesn't stop me from being a fan.
There it'sa custom as old as humanity itself. The Law dictates that a man saved by another is expected to offer to his savior a boon whose nature is unknown to one or both parties.
Here, it just means surprise me. Failing that, I'll have to try to keep surprising myself, which as you can imagine, is difficult.
