main quest should be there is to push the argonians back to their homeland.
There should at least 5 new cities, Blacklight, Mournhold, Tear, Narsis and Bodrum:
Bodrum: A town bordering Skyrim and Cyrodiil to the east, it is a first town you
come across when you go past the Riften border gate. There are a few argonian
guards in the town.
Blacklight: A northern port town bordering Skyrim to the east and it is the only town of
which hadnt been occupied by argonians. It is a main base for the dunmer resistence
faction.
Mournhold: Capital city of Morrowind, it is a largest city in the country. But
watch out for argonian soldiers/justicars, if approach them they become hostile.
Tear: It is a town along the border with Argonia. Then again argonians soldiers/ justicars may be
hostile if you come too close to them.
Narsis: A town in south-west Morrowind and it is a main headquaters
for the argonian faction. In fact the original town got destroyed but
it is recently being built by the argonian settlers and they also built
a castle south of town.
Vvardenfell: It is a now a dangerous place to go. It is full of cliff racers, ash and
lava. The whole island is a volcano and there are no towns there but it be full
of dungeons that is what is left of towns.
While traveling in Morrowind, further south you get the more you encounter
argonian soldiers/justicars. If you travel further north you get the more you
encounter cliff racers because of Vvardenfell.

