Pandemonium Fortress (Diablo II)
It serves as a base for the Angels and their mortal allies in their struggle against the forces of darkness. It is unclear whether this is a unique base, or if there are other similar to it in other places.
The Island of the Sunless SeaEdit
A quest that was cut from the original Diablo, Farnham mentions an "island where the Angels watch.". Extracting the wav files from the Diablo I disc's MPQ reveals that Farnham does, indeed, have an unused speech regarding this:
"Hey you there, c'mere, listen up!... Y'know 'bout the island where the Angels watch? Pick the right rocks, but ya better shield yer eyes -- shield everything! I know, 'cuz I been there, and -- mmmm, ale..."
Deckard Cain also has an unused speech file which speaks of the Island, transcribed as follows:
"Hmm. An island? Where Angels watched? Although Farnham's memory is often cloudy these days, that does seem familiar... perhaps the ancient Chronicles of the Sin War can help us... Ah! Yes! Here is something: In a time long forgotten, a sea of blue rested on the edge of the fiery netherworld. This was an oasis for those who acted as the watchmen over the gates of Hell. Angels and warriors of Light could use this place to heal themselves and gather their strength. It was also a staging area, where they could train and prepare for the Sin War. Legends speak of a trinity of rocks that hide the path to this... Island on the Sunless Sea."
Cain's description of the island seems to fit what we know of the Pandemonium Fortress. It is likely that the concept behind the cut "Island" quest in Diablo I became what we know now as the Pandemonium Fortress in Diablo II.