User blog comment:Woest/The Light and Darkness of the Guild/@comment-3285005-20140316034418/@comment-7418318-20140316090004

To add a bit to this, I think when Makarov talked about "dirty secrets" he was dodging the question, rather than giving his opinion about Lumen Histoire's nature.

Even without bringing possible translation errors or mis-interpretations into the matter, it'd still make sense even from just the english text.