Location from Shadow and Bone by Leigh Bardugo
A wall of impenetrable darkness splitting Ravka in half — created by the Darkling's merzost four hundred years ago, filled with eyeless volcra, and destroyed by Alina Starkov's light.
The Shadow Fold is the Darkling's greatest mistake and the Grishaverse's defining landmark. Created approximately 400 years ago when Aleksander Morozova used merzost — the forbidden power of creation — to build a weapon that would protect Grisha from persecution. Instead, it consumed the fertile Tula Valley and transformed its inhabitants into volcra. The Fold splits Ravka east and west, making the nation strategically vulnerable and economically crippled. Crossing it by sandskiff is one of the most dangerous journeys in the world. Only Alina's Sun Summoner light can repel the volcra within. She ultimately destroyed the Fold entirely, reuniting Ravka — at the cost of her powers.
A vast swath of total darkness occupying the Tula Valley. No light penetrates it. From outside, it looks like a wall of black mist. Inside: complete sensory deprivation except for the sound of volcra wings. Crossed by sandskiffs with enormous sails — the journey takes hours of silent terror.
Also known as: The Fold, The Unsea, Shadow Fold