Fixten
Why don't you also test their courage / will at the same time? Correct me if I'm wrong but the ability to apply allusions to reality by making the mind believe and apply it is similar to our world's placebo effect (believe it and therefore experience the effects). If you are able to apply it to make the mind do anything it is actually capable of, you should be able to make them lose all their power temporarily through suggestions like 'formations' and 'purifications' ect.