Betrayers' Rise

The Umbra Gates is a temple to the Betrayer Gods near Bazzoxan.

Description
Jet-black towers and a gargantuan black doors in the mountain are rising over Bazzoxan.

There are multiple barricades set up throughout the exterior and interior of the various tunnels of Bazzoxan, but things still manage to creep past and the soldiers kill them and try to fill the gaps.

There is a side entrance beyond, to the right of the Umbra Gates

History
The Umbra Gates 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, there was unity between the demonic Princes, for the purposes of fighting the Prime Deities during the Calamity.

Known Demon Princes of the Abyss include:
 * Baphomet ("The Horned King"): Demon Prince of Beasts
 * Demogorgon ("The Sibilant Beast", self-proclaimed "Prince of Demons"): Demon Prince of Madness
 * Graz'zt the Seductive ("The Prince of Pleasure"): Demon Prince of Indulgence
 * Juiblex ("The Oozing Hunger"): Demon Prince of Formlessness
 * Orcus ("The Blood Lord"): Demon Prince of Undeath
 * Yeenoghu ("The Beast of Butchery"): Demon Prince of Savagery

For the last 100 years, the Aurora Watch in Bazzoxan has been holding off whatever creatures escape the temple.

Etymology
Umbra likely comes from the Latin noun umbra, umbrae (f), which means "shadow" or "ghost", depending on the context.

Trivia

 * This article assumes that the Demon Princes of the Abyss are the same as in the Forgotten Realms canon of Dungeons & Dragons. However, given the infinite nature of the Abyss, it is entirely possible there are other Demon Princes beyond those listed here.