The Shadow Fold, also known as "the Unsea" or simply the Fold, was a swath of darkness located in the Tula Valley that split the eastern and western sides of Ravka in half. It was destroyed by Alina Starkov during the Ravkan civil war. Before its destruction, the only reliable way across it was with a Sandskiff.
The Shadow Fold was created around 400 years ago before the events of Shadow and Bone by The Darkling, using merzost, because of his want for power. However, he did not anticipate what such power of that magnitude would do to mere men, turning them into abominations generations ago. The volcra have kept the Darkling from using the Fold against his enemies as only sunlight can subdue them. The volcra being a result of the Shadow Fold are said to be "his punishment and a living testimony to his arrogance."
The land that the Fold covered was once green, fertile and rich, and had been home to many farmers and their wives and children as well as some of Ravka's richest estates.
Shadow and Bone
The Shadow Fold first appeared in the beginning when Alina Starkov and Malyen Oretsev had to go through it with their regiment when they were stationed in Kribirsk. They were supposed to finish their training in Os Kervo on the True Sea and then cross the Fold again to return home. However, they never made it through as their expedition turned deadly only 30 minutes in. The volcra usually moved in small numbers, but the sandskiff of Alina's regiment was swarmed by hundreds of them. After Alina revealed her sun summoning powers on the Fold, the sandskiff was immediately forced to return back to the drydocks in Kribirsk.
Near the end of Shadow And Bone, Alina, and The Darkling entered the Fold in a mission of destroying it, but when they reached the drydocks of Novokribirsk, the Darkling instead expanded the Fold by swallowing the town into darkness and the volcra who were kept in control by Alina's powers soon swarmed in on the people.
Siege and Storm
After the destruction of Novokribirsk by The Darkling, all crossings of the Fold had ceased.
Zoya Nazyalensky managed to sail a small skiff across the Fold on her own, desperate to see her aunt after news arrived of Novokribirsk's destruction. Upon no sign of her aunt, she traveled back again.
Alina and Mal made the crossing back with Nikolai's flying contraption after they escaped The Darkling on the True sea.
Ruin and Rising
King of Scars
After the Shadow Fold was destroyed by the Sun Summoner Alina Starkov, the volcra had dissipated, but the area still remained barren with nothing growing over the dead grey sands.
The Shadow Fold was a section of nearly impenetrable darkness that grew every year and contained volcra among other unnamed horrors. The Shadow Fold, located in the once rich Tula Valley, cuts directly across the Vy, a wide road that once stretched across the land connecting Os Alta to the port cities on Ravka's western coast.
On maps, the Shadow Fold was shown as a long, narrow lake, a stain, and sometimes just a bleak and shapeless cloud. The Fold is often labeled by its other name the Unsea intended to put soldiers and merchants at ease and encourage crossings. Animals were too noisy and easily scared for travel on the Fold, so crossings were made on sandskiffs with enormous sails that skated almost soundlessly over the dead grey sands. Traversing the Fold was the only way to provide a landlocked Ravka with critical supplies. And so skiffs were always loaded with grain, timber and raw cotton, and on the way back they would be stocked with sugar, rifles, and all manner of finished goods passing through the seaports of West Ravka.