the full thing they would say is: "we are the three cleansers. and we have been chosen to cleanse traitors like you. we have witnessed all the pathetic attempts thet you and your weakling friends have done just to stop blongus. but... with a little bit of cleansing, we will fix that."
it still is part of the lore even with no movie. what are the cleansers purpose? they cleanse the mind of any impurities in other words: they erase memories of people and makes them slaves of blongus's city. and with the huge amount of people in the city of blongus... you can say many attempted at stopping his tyranny but no one has succeded it seems.
