User blog comment:IamJakuhoRaikoben/Chapter 381: Where Demons Live, Review./@comment-3424593-20140418172109/@comment-7418318-20140418181542

Take-Over isn't just transforming, but "taking over" the enemy and their powers.

Taking a Demon's/Beast's/Animal's power into one-self so you can use them as your own is the very essence of Take-Over Magic.

And that's exactly what Mirajane did with Sayla: She took over one of her powers, but failed to take the rest too. How is that such big bullshit all of a sudden? It's the very thing she does whenever she takes over a Demon, just that it was stopped halfway (or probably earlier) through.

I can agree on the thing with the tentacle monster in the tanks being iffy, but for the reasons above, I think taking Sayla's power into herself is exactly what Take-Over was supposed to do.