Into The Rift by Clay Harmon

After defeating the mercenary army that threatened his home, Jakar sets out with Efadora - the only person left with the power to bind him - across the Rift. He hunts the cultists who enslaved him, intent on ending their trade in elemental children, but he remembers little beyond that his search begins in the legendary city of Sulian Daw. Back in Mira, the Foundry's rhidium - the rare mineral that grants them extraordinary power - has gone missing and is feared stolen by the rebellious faction that seeks to bring down the Sovereign. Ester, fledgling Smith of the Foundry, is tasked with tracking it down. If she fails, the Sovereign will rain death upon all those who oppose him, costing thousands of innocent lives.
Binding: Paperback / softback