Catalyst Moon: Incursion by Lauren L. Garcia

The One god shaped the world to exist in perfect harmony...until Seren, the second moon appeared, bringing magic and throwing humanity into chaos. Now, mages are captives, guarded by high walls and highly-trained sentinels, men and women who ingest a dangerous substance to gain an immunity to magic. Only then can they protect the world from the magic-users and abide by their oath: Honor. Service. Sacrifice. Kali, a crippled mage, travels to Whitewater City to meet with a powerful healer. When her sentinel escort is decimated by monstrous bandits, she is left in the company of a single sentinel, Stonewall, a man with nothing left but his chosen name and his faith in the gods. Together, they must survive demonic creatures, bloodthirsty nomads, and a strange magic never seen before. But with every strife comes a discovery of new landscapes within each other’s hearts.