The Rotten Vale can be divided into three sections; the third being much smaller in size.
The upper area near the starting camp is fairly open and mostly inhabited by Radobaan, Hornetaur, and Vespoid. It is mostly made up of large bony structures.
The area that can be reached by jumping from the upper section has numerous Girros. Of course, their leader Great Girros lives here, and Odogaron can also be found deeper in here. In addition, the second camp is located in this section. Effluvium is a big problem from the first portions to the deepest parts of this section. The corpses of Raphinos and, very rarely, Legiana will occasionally fall to this area.
Acid Pools and the Depths
The depths of the Rotten Vale has acid that can damage hunters. The dens of Odogaron and Vaal Hazak can be found here.
- The Rotten Vale has a deadly gas that can suffocate hunters. Called Effluvium, it is produced by a bacterium that causes dead tissue to rot rapidly. When a Hunter is exposed to Effluvium, their maximum health will be reduced.
- This gas also makes the monsters that live in the area more aggressive than usual, even timid ones.
- Giant bone structures hang above some areas that a hunter can bring down upon monsters using their Slingers.
- Above the Rotten Vale is the Coral Highlands.
- Hunters can carve the corpses of monsters in the Rotten Vale like Legiana.
- The skull of a Dalamadur can be seen in the top Rotten Vale, and in the map.￼
- The head of Dalamadur can be seen at the Base Camp.
- 8 tails of Dalamadur can be seen throughout the Rotten Vale.
- The Rotten Vale has acid puddles that damages those who stand in them.
- The Rotten Vale is the graveyard for monsters, including Elder Dragons. Monsters come to this area to die.
- Upon dying, the Elder Dragons dissolve in the effluvium, and their bioenergy accumulates in the earth before eventually crystallizing. This process made the crystalline structures seen in the Elder's Recess and Confluence of Fates.