Mommy Is the True Sea Queen

Long ago, the kingdom of Alester slew the child of the Abyssal Sea Monster, and ever since, each king has been required to offer up a princess as a sacrifice. Marina, an illegitimate daughter, agrees to take her mother's place after her half-sister Serena drugs her and sends her to the altar in her stead. Instead of perishing, she is saved by Poseidon, the Sea God, and the two share a single night together. Nine months later Marina gives birth to six extraordinary children with divine gifts, and she raises them on her own for six years before fate brings her face to face with Poseidon once more.