This is what I was thinking of to go up against the field stone walls around the dungeon walls.
The tall back ends would have to be screwed (bolted?) to the overhead beams for support since there isn’t any way to actually attach to the field stone. Maybe I will need to add short, sturdy feet extending out onto the floor space for additional support. Thick mil. plastic sheets between the wood and wall would keep the moisture from rotting the wood. All I need are more pallets.