Skyforged: A Steamborn Novel. Steamborn, #5

A past unwritten. A shadow fallen. An enemy unmasked. Time grows short to secure the desert city of Midstream. Fel struck a devastating blow, and it's only a matter of time until their next attack. Out of options, Jacob turns to the abandoned works of Charles von Atlier to create a Titan Mech. The towering machine may be just the weapon they need to protect the city. But Mordair's thirst for power is escalating.
As King of Fel he is taking full advantage of his alliance with the kingdom across the sea. Together, they're preparing a siege on Belldorn sure to split their enemies' focus. Jacob and Alice are placing all their hopes of salvation in the Titan Mech when a terrible discovery in the Red Woods proves even that won't be enough. Somehow, someway, they must strengthen their defenses. The quest to come will be their riskiest yet as they journey straight into the heart of Fel itself.