Demon's Deal: A Demon's Series Short Story

Before Sauda was a badass military assassin, she was the result of a blood contract made between a married woman, and the only person—or Demon—that could save her firstborn child.

Bilillee is at the hospital that sits on the crossroads, hoping that she'll finally give birth to a child. When the doctors can't save her baby, she prays for a miracle or anything that will help, including making a deal with the Devil. Her abusive husband agrees for her to sign a contract with a Demon to save her son in exchange for her second born child thinking that she'll never be able to carry another baby to term.
Two Years later the Demon comes back, and when Bilillee reveals that there is no second child, the Demon reveals the true payment of the contract. Now Bilillie is swept away to the Demon's world, to bear his Demon seed.