Every action has a consequence. Every bond carries weight. Mia's mistake has awakened powers that will reshape both god and mortal realms. When her brother's life slips beyond the reach of medicine, Mia Petrakis turns to the only power left: the divine. An ancient ritual book passed down through her family whispers of a way to reach the gods. One desperate invocation drags her into the Underworld. But the ritual goes wrong. Instead of summoning Hades, Mia binds the King of the Underworld to her soul, stitching their fates together with silver threads neither can break. Furious, intrigued, and bound by laws older than Olympus, Hades agrees to grant her plea... but the cost may be more than either was ready to pay. Now a god walks the mortal world in her shadow, and every step tightens the bond between them. Every heartbeat pulls them closer. Every secret threatens to unravel the fragile line between salvation and ruin. To save her family, Mia must face the truth: Some vows are forged in desperation. Others are written in destiny. And the most dangerous are the ones forged under fire. Underworld Vows is the first book in a Greek mythology-inspired fantasy romance series featuring a slow-burn mortal/god romance, accidental soul bond, forced proximity, found family, and high-stakes supernatural conflict.