Betrayers' Rise

Betrayers' Rise is a temple to the Betrayer Gods, just north of Bazzoxan.

Description
Petrayers' Rise is made of black stone and is behind the massive onyx Umbra Gates set into one of the mountains that surround Bazzoxan. It is heavily barricaded and guarded against the demons and other creatures that arise from within it. These guards, from the Aurora Watch, prevent outsiders from entering, or even approaching within 30 feet of the doors. Past the gates is a bridge which crosses a chasm full of mist, in which there can be heard threatening voices. The bridge leads to a set of double doors which are inscribed with a portrait of the Changebringer which has been defaced, though not entirely eradicated.

The interior of the temple is made of the same black stone, which is immune to Stone Shape. It has 50 foot high ceilings in the various chambers, and 20 foot high ceilings in the corridors, and is mostly unlit. The chambers within shift in their configuration and nature; two different groups entering the temple may experience a different set of rooms.

History
Betrayers' Rise was the historical seat of power on the Prime Material Plane for the Demon Princes of the Abyss, in Xhorhas. For a brief period of time during the Calamity, there was unity between the demonic Princes for the purposes of fighting the Prime Deities. It served as both temple and fortress.

As of 836 PD, for the better part of a century, the Aurora Watch in Bazzoxan has been holding off whatever creatures escape the temple.

Call of the Netherdeep
In the adventure Call of the Netherdeep, set in 836 PD, the heroes travel to Bazzoxan in the hopes of learning more about the Jewel of Three Prayers. There, they encounter various individuals who lead them to enter Betrayers' Rise. Verin Thelyss tells them that he believes that the temple may contain the solution to reclaiming Bazzoxan from the Abyssal creatures that attack the city, but that the Aurora Watch has been unsuccessful in their expeditions. He also warns them about the unpredictable, magically shifting floorplan of the temple. The specific configuration of rooms they encounter are perilous and include a mixture of Prime Deity and Betrayer God iconography.

Within the temple, the party eventually finds an ancient prayer site of the Changebringer, and experiences a vision of Alyxian.

Etymology
Regarding the Umbra Gates that enclose Betrayers' Rise: Umbra comes from the Latin noun umbra, umbrae (f), which means "shadow" or "ghost", depending on the context. It is a term used to refer to the darkest part of a shadow, where the light source is completely occluded.