Hello,
Sanctuary is a danger place, there are much outside to explore and few crazy guys to do it.
How resolve it ? greedy!
Efu have merchants at many points, they sell common and/or class itens.
What they want buy ? What they may sell ?
If have different prices for common/class itens along the merchants then we can organize "plot" traders and caravans, between places and make the underdark more seem. This can be done by buying a new item "note" from merchants, like a deal to buy a new item stock (pack) of 1000 potions, travel to other place to buy and travel back to sell. Yes it may be like quests and have a time to do.
[]s tooh