User blog comment:Omega natsu2/Chapter 368: The Third Seal, Predictions./@comment-4933386-20140120162841/@comment-24066070-20140122034202

It seems most MC members aren't wizards or at least don't possess powerful magical abilities. I think they created/kept it as a last resort to maintain their authority over wizards. Something like: "You'll obey our decisions and should you rebel against us, we'll take away your powers"

That would be an extreme measure, but considering the fact that those who score 300+ on the MPF are captain-level material in the Rune Knight army (who act as the MC's military) it is quite a smart trump card in order to maintain the upper hand should a massive revolution against them take place.

I'd say they have a way to activate it themselves without killing 3 of their own members, whether this method involves a "prayer" like OS is uncertain, but I reckon it will be similar.