Netheril Facility on Brexiella

Even amongst the Netheril, certain magics were frowned upon and the practitioners of such arts found it more convenient to conduct their magics far from their main civilization.

Thus it was that a group of warlocks, practitioners of Dark Magic,  came to settle upon Brexiella, one of the islands that form the Celastraceae  archipelago.

There they found the freedom to conduct and perfect their summoning and binding rituals, consorting and making pacts with all manner of nefarious fiends and planar entities without the fear and criticism of those who who were satisfied with the lesser arcane arts.

The Netheril were not fools however and aware of the dangers they entertained by summing demons to the material plane. So they pooled their efforts and created a mighty artifact that could banish any non-native beings from the material plane, to be activated if any summoned beings escaped their control.

The facility was abandoned when the Netheril were forced to abandon Malador and remained empty until discovered by the alatus around 400 RR.