Having just completed Act IV again on a new character, I find myself facing the same question I forgot about on countless playthroughs. There are about two or three areas in Act IV, which are alltogether inaccessible, but do seem to feature have fully interactive elements such as gates and doors, as well as killable mobs, and I am not talking about glitch spawns either. These mobs are clearly supposed to be there. While one could just consider it a nice immersion gimmick, it has always bothered me, since I assume epic or legendary items could potentially spawn in the hands of these unreachable mobs.
First, there is this area on the Fields of the Diadochi. It is clearly a planned area, as there are two mechanical traps positioned at a blocked pathway and a few Empusa or other mobs always spawn there. I always end up trying to get there by getting up and down the ramps, but you can't:
Then there's the lower Prison of Souls, which always has a Gigantes guard. The prison gates appear unlockable by the Warden of Souls key, but again,.. you can't actually get there. I suspect there to have been a Quest planned with the prisoners, that was eventually left out of the game. It would made sense to have another teleporter, such as to the various Shards of Erebus areas, connect to an area with a door that grants access to the lower level:
Finally there's the
Ninth Gate of Hell, which might perhaps be an easter egg:
Still pretty weird IMO. Initially I thought it was just there as an area signifier for an area that doesn't have a portal, but once you know how to deal with Act IV normal mobs, you'll find that Hades is not really that far from the last active portal (Hades' Palace / Persephone's Gate). As such there's not real reason for the final area to be seperate and warant a map entry with a broken portal.
All in all, this thread is pretty pointless. It doesn't really lead anywhere, but I just wanted to share my thoughts. Any other ideas and/or comments are much appreciated.