Winterglass - Her Pitiless Command, #1

In this dark fantasy retelling of the Snow Queen fairy tale, a deadly assassin must balance a tragic love triangle and her desires to free her city from the cruel clutches of the Winter Queen. The city-state Sirapirat once knew only warmth and monsoon. When the Winter Queen conquered it, she remade the land in her image, turning Sirapirat into a country of snow and unending frost. But an empire is not her only goal.
In secret, she seeks the fragments of a mirror whose power will grant her deepest desire. At her right hand is General Lussadh, who bears a mirror shard in her heart, as loyal to winter as she is plagued by her past as a traitor to her country. Tasked with locating other glass-bearers, she finds one in Nuawa, an insurgent who's forged herself into a weapon that will strike down the queen. To earn her place in the queen's army, Nuawa must enter a deadly tournament where the losers' souls are given in service to winter.
To free Sirapirat, she is prepared to make sacrifices: those she loves, herself, and the complicated bond slowly forming between her and Lussadh. If the splinter of glass in Nuawa's heart doesn't destroy her first.