User blog comment:Kogath/Monster Hunter: World Discussion/@comment-6050823-20171031044152

MHW Info: Rotten Vale and Monsters

Rotten Vale
 * The Rotten Vale is a deadly valley filled with the corpses and bones of countless monsters. This area is always in a constant state of decay, making inhospitable for most creatures. Despite this, some monsters do live in the Rotten Vale.
 * The monsters in this area are extremely hostile and won't hesitate to attack any intruders in the Rotten Vale.
 * A toxic gas leaks from the Rotten Vale, making the area more hazardous for hunters. This gas can endanger a hunter's life. This gas also makes the monsters that live in the area more aggressive than usual, even timid ones like Rafinosu.

Radobaan
 * Radobaan is a close relative of Uragaan found within the Rotten Vale.
 * It is nicknamed the "Bone Hammer Wyvern" (骨鎚竜).
 * Unlike Uragaan, Radobaan doesn't feed or adheres minerals to its body. Instead, Radobaan covers its body in the bones of other monsters in order to forge its own armor for protection against predators. However, the bones can easily be knocked off if enough damage is applied to parts of Radobaan.
 * Despite its size, Radobaan is fairly quick compared to Uragaan.
 * Radobaan feeds on the bones of dead monsters.

Giruosu and Dosugiruosu
 * Dosugiruosu is a Fanged Wyvern that resides in the Rotten Vale. It is constantly searching for corpses to feed on and is usually accompanied by Giruosu while looking for an easy meal.
 * Its fangs contain a paralyzing venom that kills prey in a single bite. This how it gets the title "Paralyzing Thief Wyvern" (痺賊竜).
 * Giruosu are quite dangerous in large groups and will get into a frenzy if they surround a hunter.

Odogaron
 * Odogaron is always hunting for its next meal. Sometimes it can be seen dragging a prey item back to its lair to feed on.
 * It'll attack anything that it encounters on sight, even if that prey item is bigger than itself.
 * It is sometimes called the "Cruel Claw Wyvern" (惨爪竜).

Legiana
 * Legiana is well-known for hunting down Rafinosu, its favorite prey, by using cold air to restrain their movement as they fly. It is sometimes called the "Wind Drifting Wyvern" (風漂竜).

Sources: http://www.capcom-germany.de/2017/10/playstation-4-beta-erste-blicke-ins-tal-der-verwesung-und-exklusive-horizon-zero-dawn-dlc-inhalte-fuer-monster-hunter-world/, https://www.famitsu.com/news/201710/31145104.html