"Visitors
The most common event at your stronghold is having a visitor arrive. There are all kinds of visitors, but they all share one thing. They can adjust your prestige and/or security just by being at your stronghold. Some visitors give good bonuses and some of these visitors can even be employed as hirelings and will stay on as long as you pay them. Others are not so great, and you can offer them one of your companions to act as an escort to their next location, or pay them to leave. Some visitors will offer rare items for sale, and some might even offer a very rare item in exchange for one of the prisoners in your dungeon. If Visitors die during their stay, the stronghold suffers a Prestige penalty for a while."
http://pillarsofeternity.gamepedia.com/Stronghold?cookieSetup=true
Btw, can you answer a question in return? Can you have simultaneous stronghold upgrades going on? I read that's a thing but it doesn't work for me.
