Drop a building on them.

You pause in a moment of sudden clarity. The building's are so dilapidated, they're on the verge of falling over! Why not just help them along that path?

You quickly dart to the back of the room, finding what appears to be a column of stone holding up the rear of the building. It sags dangerously forwards, at a worrying angle. Perhaps, if you were to remove certain parts of it...

You set to work, jimmying out looser stones with your swords blade, until the building is creaking. You are confident one more stone will collapse the entire barn. Just in time too, as you hear the heroes fast approaching. You pause in thought. How to lure them into the building, though?