bonix5231
Every person is born owing a Debt to the Underside, a drowned mirror-world beneath the sea. Once a generation, the ocean recedes during the Auction Tide, and the Underside "collects" whoever it has marked. They aren't killed. They're sold, and no one has ever bought one back.
Ilse Marrow, 15, lives in a salt-flat fishing village. Her father was collected the night the tide went out, and she is the only one who saw what took him: a figure in a clerk's coat, stamping a receipt.
She resolves to become an Assessor, one of the few licensed people allowed to walk the seabed during the Tide and negotiate with the Underside. Her secret: she was born with a Debt-Free mark, which supposedly can't exist.
The Power System: Collateral
To awaken a power (a Lien), you pledge collateral: a memory, a sense, a year of your life, a promise. The more you give up, the stronger the Lien. Liens also carry terms that limit them (only works at dusk, only on people you've lied to, and so on), and broken terms are collected with interest. Fights become battles of bookkeeping, bluffing, and deduction as much as raw power.