So, I've just reached the point in the game where I've met with Vivec, and he has given me the plans to defeat Dagoth Ur. He mentioned that I should go to Ghostgate and get a map of Red Mountain from the Buoyant Armiger, so I can locate the Citadels of the Sixth House. The problem is, I've asked every Armiger I could find at Ghostgate, and none of them gave me a map. I checked the UESP, and apparently you get the map by asking the topic "Inside the Ghostfence". However, that topic isn't available with any Armigers, so I can't get the map. Also, the quest isn't showing up in my journal, so I'm not sure if I'm missing something here.

Anyone have any help?

Do you actually need the map? Couldn't you just head on inside the Ghostfence, and begin killing the Ash Vampires? The map you're given actually isn't useful at all, and you're better off using the UESP if you need information on where the Citadels are. The first step of the quest is to actually get the map, I believe, so it would probably initiate if you killed one of the Ash Vampires. Also, make sure that you talked to Vivec about every topic. It's possible that you missed something, which would have made the 'Inside the Ghostfence' topic available.

There was a map for Red Mountain?

See, I didn't even know that and I still ripped those Ash Vampires and anyone else who got in my way a new one. It's more fun to do stuff like that without a map anyway. Red Mountain may be huge, but there really isn't anything there besides Dwemer and Daedric ruins.

It is indeed the most useless map I have seen in a long time. It's as much a map of Red Mountain as finger paintings are fine art. See for yourself: http://www.imperial-library.info/content/morrowind-map-red-mountain

I'm not really sure what could've broken to prevent you from getting this map. When talking to Vivec, asking "who can help" should add "inside the Ghostfence" to the list of topics available with the Buoyant Armigers.

You might as well just search for the citadels yourself, they aren't that hard to find. They're all Dwemer ruins so they stand out from the landscape.

Yeah, that map is extremely unhelpful. The paper map that comes with the game is1000x as useful.

You don't even need to actually go after all the Ash Vampires....you can just stroll straight up to Mr. Ur. I usually kill all the Ash Vampires so I can display their various enchanted items in my stronghold as trophies, but other than that, there's really no need for it.

But if you want to, I usually just go counterclockwise around Red Mountain to hit the 4 citadels and then hit Ur himself. As some others have said, the Dwemer ruins aren't too difficult to find.