| Category | Strongholds |
| Continent | Brucrumus |
| Region | Grashakh |
| Built | 4 Brightstar 1099 |
| Map | Inirthak |
Alluvium Deep is a privately owned prison in the Sands of Hell. The fortress-prison was built over the ruins of a sand giant keep.
Alluvium Deep was built by the Kal-Oni to serve as a holding place for silver ore mined out of the rocky slopes beneath the ruins. A keep with well-constructed vaults and laden with traps rose from the mining efforts. This place served as storage for the silver until it could be taken down the Dargirth and then to what was a fishing village called Paradomea (c.f. Paradomea City). When these mines were expended, the place became a prison for the more dangerous elements of the Kal-Oni Empire. When this empire ended, the place continued to take in prisoners from anyone seeking to rid themselves of criminals. In 1266, the Kal-Oni Empire fell and with it ensued petty wars over the former state property. No longer a state property, Alluvium Deep fell into the hands of the prison overseer and his lieutenants. This group took the name Alluvium Wardens. They held the place for two decades, losing it to a mercenary force backed by the Hannanâtha. This powerful Bathor family seized the place to release one of their family members. Many of the Alluvium Wardens escaped into Drarthiel. The Hannanâthas held the place for six years.
In 1293, Alluvium Deep was struck by an unnatural earthquake which broke open many cells. Behind this magical attack were the Alluvium Wardens. They attacked the place from underneath with the aid of 500 deep gnome mercenaries from Bolip-Stalacite. House Hannanâtha, losing money on the Alluvium Deep prison, decided not to mount an attack to recover the place. The Hannanâthas suffered badly over the following years as its members were murdered by the Gray Matrix. House Hannanâtha used their wealth to buy off the Gray Matrix and threatened to turn them on their former employers, the Alluvium Wardens. A peace was brokered between the two and in time they established a healthy business relationship.
The Alluvium Wardens own and operate Alluvium Deep. Many criminals of Bathor, Council of Bile, and Paradomea are sent to this place to work off their sentence. The prison takes criminals from anyone. Many come here and die here. Most perish in the salt mines and mineral deposits, while others succumb to death in Alluvium Deep's notorious gladiator pits. These fighting arenas of the prison offer a means to shorten the sentence of prisoners who prove their prowess in combat.
In 1454, the adventuring group Black Banner broke into the prison's lower cell blocks, freeing some prisoners and making off with relics of the place's original builders. One of the freed prisoners was a Tragaran named Garn.