The Sarantine Mosaic book set 1&2 by Guy Gavriel Kay

Caius Crispus, known as Crispin, is a master mosaicist, creating beautiful art with colored stones and glass. Still grieving the loss of his family, he lives only for his craft—until an imperial summons draws him east to the fabled city. Bearing with him a Queen’s secret mission and seductive promise, and a talisman from an alchemist, Crispin crosses a land of pagan ritual and mortal danger, confronting legends and dark magic.

Once in Sarantium, with its taverns and gilded sanctuaries, chariot races and palaces, intrigues and violence, Crispin must find his own source of power in order to survive. He finds it, unexpectedly, high on the scaffolding of his own greatest creation.

In the golden city of Sarantium, a renowned mosaicist seeks to fill his artistic ambitions and his destiny high upon a dome intended to be the emperor’s enduring sanctuary and legacy.

The beauty and solitude of Crispin’s work cannot protect him from the dangerous intrigues of court and city, swirling with rumors of war and conspiracy, while otherworldly fires mysteriously flicker and disappear in the streets at night. The emperor is plotting a conquest of Crispin’s homeland to regain an empire. And with his fate entwined with that of his royal benefactor, Crispin’s loyalties come with a very high price.

And another voyager has come to the imperial city: Rustem of Kerakek, a physician from an eastern desert kingdom, determined to find his own fate amid the shifting, treacherous currents of passion and violence that define Sarantium.