The Great Blight is a corruption of the land in the north of the world, extending from Shayol Ghul.
The Great Blight is rotten and bare land, created by the influence of the Dark One over the world. All the earth has turned to dust and very few flora live here. It is a very dry land, as despite the existence of the Thousand Lakes of Malkier, their waters are poisonous and monsters live within them. It also has numerous high mountains which run horizontally in a range across nearly the entire Blight. They are known as the Mountains of Dhoom.
It is revealed by Graendal that the red color of the soil is the result of large quantities of iron present in it. It is also revealed that the climate of the Blight is hot and dry, though the temperature gets colder the further north one goes.
The Great Blight lies north of the Westlands, the Aiel Waste, and Shara. The Mountains of Dhoom separate the Westlands from it. The Aiel Waste just flows over to the Blight, but Shadowspawn will rarely enter the Waste. It is unknown if there are mountains separating Shara from the Blight, due to the secretive nature of this nation.
The Great Blight is created by the Dark One. His influence over the land surrounding Shayol Ghul kills almost every form of life. As his grip on reality grows stronger, more land is corrupted, as evidenced by the taking of Malkier. It has also been reported that, both recently and earlier in history, the Blight has receded a few miles. This is, however, very unusual.
For thousands of years, Aiel male channelers journeyed to the Blight to fight the Dark One as a matter of toh. For thousands of years, society assumed that these men died- either to the taint or Shadowspawn. However, as Tarmon Gai'don approaches, red-veiled Aiel have begun to invade from the Blight. They appear as men, but something is wrong with them.
Shayol Ghul lies in the Great Blight, north of Arafel. Here, the Pattern is at its thinnest and the influence of the Dark One is the greatest. It is a very high mountain whose top is shrouded in the clouds and where the temperature is very low. Without the aid of the One Power to get here, it is almost impossible to travel to Shayol Ghul.
A warped city lies within the Blight close to Shayol Ghul, referred to as "the Town" by its inhabitants. Virtually all of it's inhabitants are servants of the Shadow, and the Samma N'Sei in particular make their homes there. The Forsaken are known to visit it from time to time as needed.
In the Great Blight there is a huge Fortress, which was the headquarters of Ishamael/Moridin. It is mentioned to be in the North Eastern Blight, so presumably north of Shara or the Waste. It is completed with advanced stonework and a slave community outside of it, used to help build it and to cultivate camps around the fortress, to provide food.
Most probably it is an old fortress that Ishamael built while he was free during the Trolloc Wars or Artur Hawkwing's time. Inside the fortress there are chambers full of angreal and ter'angreal, and there are kept many books full of Dark prophecies.
Fauna and Flora
Although it is a bare land, the Great Blight is home to several creatures and some unusual plants. Most of them were created by Aginor in the War of Power, and are able to survive in the harsh conditions of the Blight. All of them appear to be incredibly deadly, and are best avoided.
The most well-known inhabitants of the Blight are Shadowspawn, including Trollocs, Myrddraal, and Worms. No humans live in the Blight, outside of the Town or Ishamael's Fortress, because of the harsh conditions.
Sticks are animals that look like branches of a tree, but try to strangle people who walk by them. The trees seem fleshy, rather than woody like the trees in the south.
After the Last Battle and the new sealing of the Bore by the Dragon the flora of the Blight rapidly reverted to the typical one of the mountain grasslands in spring.
The Great Blight extends eastwards across the northern boundaries of both the Aiel Waste and Shara as well, and some theorize that it even extends across the ocean floor (giving rise to the body of water known as the Dead Sea) to the Seanchan continent, where it is known as the Lesser Blight.