The Girl and the Moon (Book of the Ice #3) by Mark Lawrence

Everything seems differen in the green world, but some things remain the same: Yaz's enemies are bent on her destruction.

To stand a chance, Yaz will need the help of the nuns of the Convent of Sweet Mary - if they don't execute her first.

But there is a greater danger: their fates, and the fates of those struggling to survive out on the ice, hang from the Moon, and the battle to save the moon centres on the Ark of the Missing. Everyone wants Yaz to be the key that will open the Ark. But sometimes wanting isn't enough.