My .02 dollars (fwiw):

Jo discovers a world beyond the glowing walls of the city called the Hypogean, a magic market where citizens can trade for precious commodities. A cure for cancer or saving the life of a daughter can be had... for a price.

Jo swears to never use the Hypogean. But as her friends start using it, she realizes she can't trust them. When her girlfriend, NAME, falls ill and her body begins to petrify, Jo is forced to the Hypogean and is offered a cure for NAME... at the cost of her own body.

Unable to afford such a payment, she decides to game the system. But as her plans take effect, she realizes that it will take more than will to topple the Hypogean... it will take magic.

HYPOGEAN is complete at...