From the description:
This place was constructed over 200 years ago for a local lord. The guards here would collect tolls from people using the road and watch the surrounding countryside for signs of a hostile force of goblins moving into the lands. As the area became more settled, the need for the post decreased and it was abandoned.
A number of months ago, a small bandit gang took up residence in the post. They traveled the land, attacking merchants and raiding small villages and farmsteads. After their raids, they fled to this place, counting on its remote location to keep them hidden. In the case of attack, the bandits used the tower to give them warning and time to prepare a defense or flee.