Temple of the Damned

The Temples of the Damned are unholy places of varying purpose, but mostly related to Necromancy, first used by the Horde and then the Scourge.

In Warcraft: Orcs & Humans
The first Temple of the Damned was a walled Orc base mostly composed of temples constructed in Azeroth, but it was destroyed in the First War by the human forces of Stormwind.

In Warcraft II
Later Temples of the Damned — called Grombolar, or bowels of the giant in the Orcish tongue — are the cabalistic dwellings of the dead. Created by Gul'dan to house his blasphemous Death Knights, the Temples were formed from petrified carcasses of the race of giants that inhabited the Orcish homeworld. The subterranean labyrinth of the Temple contains the fetid halls where the Death Knights dwell and study their depraved necromancy on fallen warriors reaped from the battlefields above. Note that the symbol on one of the boulders is a Triforce from the legend of Zelda series.

In Warcraft III
In the Third War, the Scourge took over the structures. Once used by the orcish horde to channel demonic energies, the Scourge has now reclaimed this powerful edifice. From the Temple the insidious necromancers emerge to animate fallen corpses and the tormented spirits of the banshees are called into service.

In World of Warcraft
In World of Warcraft, the Undercity's Magic Quarter has a Temple of the Damned in it.