The Book of Transformations by Mark Charan Newton

A new and corrupt Emperor seeks to rebuild the ancient structures of Villjamur to give the people of the city hope in the face of great upheaval and an oppressing ice age. But when a stranger called Shalev arrives, empowering a militant underground movement, crime and terror becomes rampant. The Inquisition is always one step behind, and military resources are spread thinly across the Empire. So Emperor Urtica calls upon cultists to help construct a group to eliminate those involved with the uprising, and calm the populace.

But there's more to The Villjamur Knights than just phenomenal skills and abilities - each have a secret that, if exposed, could destroy everything they represent. Investigator Fulcrom of the Villjamur Inquisition is given the unenviable task of managing the Knights', but his own skills are tested when a mysterious priest, who has travelled from beyond the fringes of the Empire, seeks his help. The priest's existence threatens the church, and his quest promises to unweave the fabric of the world.

And in a distant corner of the Empire, the enigmatic cultist Dartun Sur steps back into this world, having witnessed horrors beyond his imagination. Broken, altered, he and the remnants of his cultist order are heading back to Villjamur. And all eyes turn to the Sanctuary City, for Villjamur's ancient legends are about to be shattered...

This book is part of the "Legends of the Red Sun" series.
Here are some other books from this series: