I would suggest a building such as an inn that allows recruited adventurers to train and slowly gain experience.
nhazelbaker
Short explination:when doing the "escorting the princess from the inn to manor quest, I enexpectedly failed the quest after entering and exiting my capital. Detailed explanation quest came from an inn four tiles east of my capital with the destination being two tiles west. Upon receiving the quest I right clicked on the destination to autopath my sovereign and the princess. The pathing took the two units through my capital city. upon reaching t
I attacked an opponents city and captured it. The city's border remained yellow while my factions border color was blue. After one turn the correct color showed. This lead me to briefly believe that I had not captured the city until I found that I was able to interact with the build screen.