In the Demon Spawn War (8972 GE - 9493 GE), Pulax was the marshaling area for the horde serving Zuggtmoy. Over five decades it grew to hold a number of demon fortresses and one central citadel that served as the abode of their demon lord. The algae clogged pond around this citadel served not only as a moat but also the rift linking the Abyssal world Mycorji with Bal-Kriav. This rift, like others opened in the Demon Spawn War, was the invasion route that the demons used to invade the region Faeglor and launch attacks into adjacent subterranean regions.
Lake Azu'phis of this area is where the first green slimes were born. After the rift was closed, it lost its ability to make them, but by that point there were thousands of them creeping off into the Underdark. Pulax has many relics of the demons that once ran amok here. The most noticeable of these are the fungal vats. These were used to quicken the population growth of slimes, molds, and puddings. Some of these are still visible, though most are buried under fungi, mushrooms, and other Underdark plant life. These vats were also used to forge the first spore weapons.