The prison healer / Lynette Noni.

"Seventeen-year-old Kiva Meridan has spent the last ten years fighting for survival in the notorious death prison, Zalindov, working as the prison healer. When the Rebel Queen is captured, Kiva is charged with keeping the terminally ill woman alive long enough for her to undergo the Trial by Ordeal - a series of elemental challenges against the torments of air, fire, water and earth, assigned to only the most dangerous of criminals. Then a coded message from Kiva's family arrives, containing a single order - Don't let her die. We are coming. Aware that the Trials will kill the sickly queen, Kiva risks her own life to volunteer in her place. If she succeeds, both she and the queen will be granted their freedom. But no one has ever survived. With an incurable plague sweeping Zalindov, a mysterious new inmate fighting for Kiva's heart, and a prison rebellion brewing, Kiva can't escape the terrible feeling that her trials have only just begun." -- Publisher's website.