I don't know how long I searched for the sewer system under Balmora Expansion. I could have just opened the mod in the construction set, but I ended up finding it thanks to a user's helpful tip on Planet Elder Scrolls. There are actually three entrances to the Undercity that I know of now, but one's hard to find. I only saw it once, when I left through it, and I couldn't find it again afterwards (it's in the hills outside of Balmora). The easiest one to use is the one in Carnithus' house on the east side of town, but it's only open from dusk 'til dawn, since the Undercity is a settlement of vampires. Another entrance that has no daylight restriction is behind a locked door in Zakothre's General Store, but Zakothre is constantly right there in sight of the door, so you need to be practically invisible to unlock it without getting reported.
I have a problem with a couple of locations in Balmora Expansion and other mods, in which I enter an interior and it's pitch black, and no light spell or night eye has any effect, but I can see fire effects. I'm not sure what causes it, but if I go to other locations for a while, I can usually come back later and the lighting is normal again.
The Undercity is pretty interesting (though not as large or imaginative as the Undercity in WoW), and has a few quests for the non-hostile vampires there, which you don't need to be a vampire to complete, several shops with unique items on a goth or vampire theme, a nightclub that sells some new beverages, and another player home as a quest reward, with a pretty unique design and new textures for it. If you want a dark, evil-looking lair that's not a cave or tomb, this compact but elegant home with black marble columns and vaulted ceilings may be the place for you.
The Undercity is in a section of sewers that are copied from the Mournhold sewers, complete with goblins, but one section has an unusually large concentration of goblins that was a welcome challenge after so much of the usual Morrowind combat being only 1 or 2 enemies at a time.
I'm not a vampire, but I'm planning to become one at some point, to go through some of the quests of one of the clans, because I like quests. I've already killed the leader of one of the three vampire clans as part of a quest, but it's not the clan I would have joined anyway. Just like the Great Houses, there are three vampire clans, each focusing on one of the three playstyles in the game: fighter, thief, and magic-user. The leader I killed was from the Berne clan, the ones who focus on stealth, and I'd be joining the magic-user clan, the Aundae.
In order to get infected, since I'm currently immune to common diseases, I'll have to make a spell, potion, or enchanted item with Weakness to Common Disease, and go fight some vampires of the clan whose bloodline I want to be a part of.
Inconsistent hostiles
Not sure why this happens, or if this is a common thing, but most of the time lately, when I approach NPCs out in the wild or in caves, shrines, etc., they don't turn hostile immediately. I often engage in conversation with them, only to find out that they're Barbarians or Mabrigashes (Ashlander witches), both of which are hostile. Only after a few seconds have passed do they turn hostile. I'm not a stealthy sort, because I like to make sure an NPC is actually hostile before I attack, or I may kill an innocent person, and since there's no colour-coded indicator like in other games (like WoW), this means I have to wait for them to attack me first. I may have to install Fliggerty's Enhanced Detection mod, which includes a spell to "detect enemy", defined as "any creatures or NPCs that are currently hostile towards you, or have fight settings of at least 80, which means they are likely to attack you on sight."
In one case, one of the Dunmer strongholds whose Propylon chamber I teleported to was occupied by a coven of witches. They were all hostile to me except one. She never attacked, so I left her alone. She didn't have unique information or offer any services, but maybe she's a part of some quest somewhere. I thought one thing she said was funny, though (I assume all witches say this) about my trade: "The Temple calls my patrons the bad Daedra, and perhaps they aren't very nice... But I guess I'm not very nice, either." Well, hey, at least you don't attack adventurers on sight! She also offered to teach me something about summonings, but no such topics appeared in her list, so who knows? Maybe that's what she meant about not being very nice. Offering to teach me something, but giving no way to ask her about it.
In another, more bizarre instance, I entered Kagaruhn from the upstairs door after jumping onto the roof, and upon entering I saw what looked like an Ash Ghoul standing in the room down the hall, with his back to me. I snuck up behind him and initiated conversation, and he had some things to say to me (he was one of those one of those named guys, the ones whose first names are all "Dagoth", or else "Dagoth" is some kind of title like "Darth" is in Star Wars), so I thought maybe I was supposed to be talking to him. Except he also had barter and repair options. which I don't think he was supposed to be offering. I checked to see what he had for sale, out of curiosity, and it appeared to be the items I'd expect to find on his dead body after I kill him -- most specifically his heart. I purchased his heart, and he said, "Thank you, come again." Then he attacked me when I stopped talking to him.
Temple quests
A lot of the Temple quests are just "go here and cure this person's disease", but there are some clever and refreshing ones, which require some actual thinking to figure out, like the one in the Puzzle Canal, and the one where you go to Mount Kand and have to answer riddles given by atronachs (though that one you can cheat if you've picked up one of the coloured books of riddles scattered around the game, one of which contains the answers. I didn't have that book with me when I did it, though, so I had to do it the hard way, which I liked better anyway.
The one that I thought was funniest was the pilgrimage to Maar Gan, where you find Darth Maul just standing around in the foyer (actually a dremora -- they all have that red and black horned head style in Morrowind), and if you talk to him, he says, "If you are a pilgrim, read the inscription on the stupid rock." He does this even if you're not on the quest. You see a few of these daedra around the game who are bound to Vivec's service, and are very grumpy and sarcastic about it, which I find amusing.
Main quest interference
Without naming names, so as to avoid spoilers, I was more or less forced to progress further than I'd planned in the main quest, due to reaching the point where certain parties who shall remain nameless become hostile toward you, and refuse to allow you to do their quests. This was despite having held back at the warned "point of no return". The NPC said very clearly "Are you sure you want to do this? You might want to take care of your business with the other party before you accept this action," so I said "No, don't do it yet," and went off to do my business, but they acted like I had accepted it anyway!
Luckily, this period of bad graces is relatively short, once you go off and do a few tasks and meet Lord Vivec, and everything goes back to normal. In my case, I had put the main quest off so long (I was past level 40 and had 51 reputation points by this time), that the "shortcut" option was open to me, in which the Wise Woman expresses concern that I haven't fulfilled the prophecies yet, and that I should go talk to someone in the Temple High Fane. Apparently you can entirely skip the trials involving all the Ashlander tribes and the Great Houses and get sent to Vivec directly. But I ended up doing most of the trials anyway, just because they offered such nice rewards, and because I like quests.
Dungeon crawl mods
I was browsing through some more mod lists, specifically one devoted to mods that add single dungeons to raid and loot, and one caught my eye: Qwert's House of Madness, which boasted a 100-level "randomly generated" dungeon just outside of Hla Oad. 100 levels? Randomly generated? I wondered how that was possible in the game. But what it actually meant was that the dungeon was randomly generated with an external program called GenMod, which is designed to allow quick and easy generation of Morrowind interiors, and saves ESPs to which you can add further detail in the normal construction set.
So Qwert said s/he generated this dungeon to celebrate the release of a new version of this program, and didn't even know what all 100 levels contained. Now normally, I prefer well-designed and carefully crafted environments to explore, but I was well aware that this was not designed for that, so I took it for what it was. This had in mind other hack & slash type RPGs instead, not something you explore and admire, just something very obviously game-y that you hack your way through and loot and pillage. Some of the floor plans really did resemble something you might see in a classic computer game featuring random dungeons like Rogue or Nethack, or maybe a pencil and paper RPG whose focus wasn't on realistic architecture.
It featured many new types of enemy (all monsters, no NPCs), with different abilities and stats, some of which were very tough, like bosses, though all using the stock vanilla Morrowind meshes. It was an interesting change of pace. The levels are absolutely packed with monsters, of all kinds, from kwama workers to skeletons to dwemer centurions and so on and so on. There is also no theme or unifying design to the levels, as all types of containers and furniture appeared side by side together (i.e. a dunmer chest, next to a mine cart, next to a dwemer cabinet, next to an upper class bed, etc.) This random assortment also extended to the architecture itself, as the levels I explored were comprised of Telvanni mushroom interiors, Redoran interiors, and Daedric shrine interiors, though the architecture was consistent within a single level (no mix and match on a single level, in other words).
I worked my way through the first 6 levels of the dungeon, having to exit after every two levels to unload my loot. But the first time I went out and came back, I was very disappointed to find that all the monsters had respawned already. I hacked my way through to the next level doors quickly that time, but the next time I headed out to unload, I stopped by the spellmaker and made a few new spells. I made three new damage spells: absorb health, shock damage, and poison, all between 100-150 damage points over 5-10 seconds, and having the widest possible range (50...feet? Yards? Meters? I'll just say "units"). I also made a 50-unit-wide soul trap spell, and picked up a bunch of empty soul gems that had been gathering dust in one of my bases. The spells worked beautifully, taking out entire roomfuls of monsters at once, and filling up about a dozen soul gems per fight.
It was definitely useful for leveling up my enchanting, as I used the filled gems to recharge some of my magic items I had used in the first couple of levels before I made the spells. But even though these were perfectly valid spells that anyone can make in the vanilla game, they felt a little too overpowered, and removed the challenge from the dungeon, so I probably shouldn't have made them. They'd certainly be far too powerful for a normal Morrowind dungeon or typical encounter, considering how sparsely populated and spread out the NPCs are in them, where you rarely ever fight more than 1 or 2 enemies at a time. The most powerful thing about these wide-range spells is that they don't even need to hit an enemy directly -- I can cast it against a wall or the floor in the middle of a room, and it affects everything within the 50-unit radius. These spells are like going into a bandit lair and just tossing grenades inside, and then going in to loot the bodies. I don't recommend it, as it'll take away the fun. I might still keep the wide-range absorb health spell in reserve for emergencies if I get ganked by a crowd of mobs, because the more mobs that are attacking me, the more health I'm leeching into myself.
The way the House of Madness dungeon is set up, from what I've determined so far, is that level 1 has a door to level 2 and a trapdoor to level 10. I haven't gone down to level 10, but I expect that there's another trapdoor on level 10 leading to level 20, and so on. From what the readme file says, there are also some kind of activators on every 10th level, so you can choose to teleport from the surface directly to any of the levels you flip that switch for, once you've been down there.
Qwert also made another 100-level dungeon called The Undead Dungeons near Seyda Neen. But those turn out to be the smaller of Qwert's dungeons, as it turns out s/he also created The House of 6 Pains, which is 500 levels deep, and The Dwemer Graveyard, a dwarven ruin that's 1000 levels deep!! Unbelievable! And I thought the dungeons in the Oblivion mod The Lost Spires were huge! Why haven't I ever seen a tool like GenMod for Oblivion?
Better Bodies robe fix
So, I never did figure out how to convert the BB dresses and gowns into proper robes. The game just silently exited whenever I tried to run my mod that changed them from "shirts" to "robes". I tried renaming the body parts in NIFskope, and of course I had to make new "body parts" for the NIFs in the construction set, but it wouldn't work, and I don't know why.
On the other hand, I think I might have a faint idea of why these gowns weren't defined as robes in the first place. From some comments that I managed to find after scrounging through ancient search results, it appears that robes, both vanilla and BB, are made to replace the entire upper body (and possibly lower body as well), and for some reason it's not practical to make a robe with a low neckline or bare shoulders, so they had to be defined as shirts.
So, since I really wanted to use these clothes, and using them meant I lost several enchanting slots due to clothing overlapping or covering up what I don't want covered up, or not covering up what I do want covered up, I just made special copies of these gowns in the construction set with multiple enchants built into them -- the same enchantments I purchased or would have purchased on multiple items under normal circumstances.
An effect of this is that those glasses (the ones I hadn't been using because they made my neck disappear) worked properly. Apparantly it was another one of those cover/not cover conflicts with my vanilla attire.