Crystallia: Flower of Twilight, Part One (Crystallia, Flower of Twilight Book 1)

Adia lives in isolation, training under her sister Emelyn, a renowned sorceress. Their days pass in peace, far away from the troubles of the world, until one day her sister goes missing and visitors - some welcome, some not - happen upon her doorstep. Now separated from Em, Adia must make use of what she's learned to survive and understand the mysteries her sister left behind.

Along the way she meets Sage and Awst, two mercenaries who help her search for her sister. Soon after her journey starts Adia finds herself caught in a strange alternate world at night - the world of Dreams, Phantasmagoria. There she finds nightmares - dark creatures who attack dreamers, and meets one of the people who fights against them, a grumpy rogue named Razan.