I know for sure that you don't lose the stronghold, as I have the fighter stronghold, then exported him out and imported in my necro and I still have that stronghold.
As for getting the other one, I'm not sure yet cuz I haven't tried it. Although I do know that there's hacks out there that allow you to get multiple strongholds (all of 'em but the Cleric one I believe).
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-Nex, da Evyl Jesta
