User blog comment:Miskos3/Fairy Tail Chapter 490: Fairy Tail Zerø, Review/@comment-5268982-20160622085020/@comment-7418318-20160622112855

With convenient I didn't mean the intended purpose of getting Mavis and Zeref together and tossing Acno away. That is as you said a good and smart move, albeit a risky one, considering she didn't even test the spell so far, but hey, that just tells us a bit more about Irene's personality, so that's fine too. What I meant with convenience is the rest.

If not for the spell, FT and their allies would have needed to first defeat Larcade and his army, then a few days to regroup at Magnolia, makes plans and split up again to get to where they are now, but instead *whoosh* one spell and the game-board is set up for the next stage on one fell swoop by Mashima, without needing to make any transition. ^^ It was a good way to bypass that, but still also very convenient.