Sage of Hope and Ruin by Riley Knight

The walls close in. Hope lies beyond the world’s end.

Aethra has no name, no parents, no home. Taken in by a secretive mentor, she’s taught to survive by robbing others of their coin – until the day he betrays her.
Saddled with debt even a noble couldn’t repay, Aethra is offered a chance to shake off the underworld elite who hunt her. She must steal the church’s most precious bloodstone on the day of their most holy festival.
But Aethra is a con artist, not a thief. When her attempt fails, she’s met not by the headsman but the king. In exchange for her freedom, she’s given a job:

Join a team on a quest to travel beyond the world’s end, and stop its spread. A quest sure to end in their deaths.
No ordinary men would accept such an offer. Least of all the assassin with a silver tongue and the heretic with dark secrets – but Aethra has no choice but to follow them unto the end.

Throne of Glass meets the Infernal Devices in this slow burn epic romantasy inspired by Greek Mythology.