- "In the Shadow Lands beyond Asshai, they say there are fields of Ghost Grass, with stalks as pale as milk that glow in the night, murders all other grass. The Dothraki believe that one day, it'll cover everything, that's the way the world will end."
- ―Ser Jorah Mormont
On their travels east, Jorah Mormont tells Daenerys that the Shadow Lands are said to be covered by "ghost grass", a form of grass that, in Dothraki belief, will overrun the green grass of the Dothraki Sea and spell the end of the world.
In the books
In the A Song of Ice and Fire novels, the Shadow Lands are a mountainous region beyond Asshai and one of the most remote locations of the Known world. The ruins of Stygai, "the city of night" are found at its heart. To go to Asshai is sometimes described as to "pass beneath the Shadow", though what exactly the Shadow is, or what is casting it, nobody seems to know. The region is inhabited, by a people known as "Shadow Men", who are tattooed and hide their faces behind red lacquer masks. Shadow Men occasionally come to trade at Vaes Dothrak, where Daenerys sees them. Whether the inhabitants of Asshai are considered Shadow Men or not is not revealed.
The Lands of Ice and Fire map book (which features a significantly different outline of eastern Essos than the TV Series) revealed that the Shadow Lands are a large, triangular peninsula that juts out from mainland Essos into the Jade Sea. The entire region seems to be extremely mountainous. The tip of the peninsula points roughly southwest, with Asshai located at its narrowest point. The Ash River, which empties into the sea at Asshai, flows through the mountains of the Shadow Lands before reaching the city. The World of Ice and Fire elaborated only a little on the nature of the Shadow Lands: the mountains are so tall that the canyons and valleys within, including that of the Ash, see light only at high noon, and that the region is barren of all benign life. Ghost grass is the only plant that grows there, monsters are said to lurk everywhere, and the fish of the river Ash (whose waters are black during the day and glow green at night) are so poisonous that only fools and Shadowbinders dare eat their flesh. The region is rich in minerals, however, and Asshai's wealth sustained by the exportation of precious metals, gems, and dragonglass. The book again did not elaborate on what "the Shadow" is. Although there is a vague implication that it is a euphemism for the height of the Shadowlands' mountains and the unsettling black stone that Asshai is constructed from, this is not confirmed.
The known world
The Further East of Essos