FORCE FIELD TRAP
On the world where the Sangreal had been hidden, Morgan Le Fay had put in place several safeguards to ensure that the key to Merlin's weapon could only be claimed by the most virtuous and true of spirit. One of Morgan's tests was a force field trap, designed to exploit the characteristic of greed. A treasure chest in the forest enticed visitors, and a person approaching it would expect to find treasure inside. However when the chest was opened, it held nothing, and instead triggered an invisible one-way force field, trapping the individual inside. When SG-1 came upon the chest in the forest, they found that Ba'al had arrived before them, but without sufficient warning, they too entered the trap that had already been triggered by Ba'al. To reverse the trap, one must reverse the impetus. The opposite of greed is charity, and instead of taking something from the chest, something must be sacrificed. Each person donated a personal item to the chest, including a pen from Daniel, a hat from Mitchell, a ring from Osric, a knife from Ba'al, and an electric hairdryer from Vala. When the chest was closed, the force field instantly deactivated, freeing them. By successfully escaping from the force field trap, SG-1 had demonstrated charity over greed as described in the Parchment of Virtues.
Episode Reference: The Quest