SureAI

As the title says this is trivial question thats mostly pointless but is still nagging me. So in Rock Shelter where you go to collect that one bounty from the wildmage there is a little gate that leads to a room with some loot and a chest. Within there is also a lever and chain that seems to open a hidden door. But I cant seem to figure out how to get into the chamber. Like I said stupid question but its bugging me.

On the spot where you find and kill the boss of the dungeon and where you find the main-loot of this dungeon you can open a shortcut to the entrance... or first to this caged treasure... then you can open the cage from the inside with the lever...