User blog comment:LordLuminous/Fairy Tail Chapter 411 Theories and Predictions/@comment-9595671-20141201080823

You know there's one other possibility I've noticed related to Face, its been said the whole time it erases magic, but what if that's not actually true? This was said by Michello, and he was never a chairman like Crawford was, meaning Crawford may have known something the other council members didn't know.

I do know it seems unlikely, but what if the other Council members were told it was a magic erasing bomb but the chairman knew that it was really the opposite, a magic amplifying bomb? If that was the case Crawford would have been aiding the wizards rather than Tartarus, so once the Face goes off Tartarus would assume they've achieved victory only to see Fairy Tail's magic isn't gone and is actually even stronger.

It makes more sense than their curses being sealed when Face's power activates as that leans more toward being stupid which they clearly are not, but having the wrong information on what Face can do would make more sense as they would have simply been fooled or tricked.

And if that doesn't apply then it could be that Face does erase everyone's magic allowing END to be freed, but then Lumen Histoire basically hits the reset button causing all the magic to come back catching all the demons off guard. Considering Hades told Natsu to give this message to Makarov, I think Hades knew of this loophole (possibly because his soul was trapped in Franmalth for so long) and Mavis told him what Lumen Histoire's powers were.