This is an updated version of CDEP FanaCeya (http://oblivion.nexusmods.com/mods/14036/?); all I've done is fix a number of bugs (see the changelog). From the original readme:

Description
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The CDEP (Community Dungeon Expansion Project) is a joint effort to enhance Oblivion's generated dungeons by adding custom content to each one, hand-placed artistically by talented modders. This mod itself expands Fanacasecul, Ceyatatar, and the Haynote Caverns, and adds a hubway connecting the three.

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Areas modified:

Fanacasecul: Fanacasecul is like many other Oblivion dungeons - quite small. In order to expand the experience of Oblivion a bit, the dungeon has been expanded to 3 levels.

Ceyatatar: Two levels added, and a backstory to its denizens has been added also. Surface entrance collapsed, but two other entrances remain.

Haynote: Primary purpose is the alternate entrance to Ceyatatar, but more shall be added here in later versions.

Additional notes:

This mod doesn't have any extra files required, and doesn't require anything besides Oblivion.esm. If you're updating, I recommend doing a clean save.

I've been using this mod for years alongside ~170 other mods, including FCOM, and I haven't noted any major conflicts. It is not compatible with Hentai Mania - that mod copies the changes made to Fanacasecul from this mod (I don't use HM; I just happened to find this out when I was doing editing for The Ayleid Steps). OOO does make the conjurers in Ceyatatar a good deal more powerful, and adds new enemies as well, but doesn't remove the Daedric Cultists.

If you like this mod, you should also check out CDEP Underpall (http://oblivion.nexusmods.com/mods/13939) and Better Dungeons (http://oblivion.nexusmods.com/mods/40392), both of which are compatible.


Known Issues
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There are still a number of overlapping tiles in the Crystal Caverns; fixing them would require a lot more work than it's worth (basically, rebuilding half that cell). A few tiles in the bottom level of Ceyatatar also overlap; since it's very minor and hard to see in the CS, I've decided to let them go.


History
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0.8
* Fixed some misaligned tiles in Fanacasecul.
* Various minor tweaks and fixes.
* Cleaned an ITM record.

0.7
* Fixed the entrance to Fanacasecul (oops).
* Grounded/adjusted a few containers, and adjusted a few architecture pieces in Fanacasecul.

0.6
* Fixed the interior and exterior doors to Fanacasecul and Ceyatatar (for real this time, using TES4Edit).
* Fixed a script bug that prevented one of the doors from opening when the riddles were answered correctly.
* Fixed a few wild edits.

0.5
* Fixed the interior door to Fanacasecul so the game doesn't crash when that cell loads (I had to duplicate the door - an OBSE script would've been easier, but hey...).
* Reduced the size of the statue in Haynote Winding Sump so it doesn't clip into the ceiling.
* Closed off a gap in the Hubway that granted access to areas outside the cave.
* Added killboxes at the bottom of the chasm in the Crystal Caves.
* Restored a bunch of deleted vanilla containers in Haynote Cave and Ceyatatar to avoid conflicts with other mods.
* Adjusted some overlapping cave pieces in the Crystal Caverns.
* Adjusted some clipping containers and roots.
* Adjusted a couple misaligned doors.
* Fixed some typos in the books/notes.
* Added the {{C.Light}} tag.
* Cleaned the esp with TES4Edit.