Erza and Mirajane visit Crawford, the former Magic Council chairman, and fall into Tartaros's trap. And in exchange for information on Tartaros, Doranbolt frees all the members of Oracion Seis!
It's a weapon that would destroy 
all magic over the whole continent.
إنّه سلاحٌ من شأنه أن يدمّر كلّ السّحر الموجود على وجه القارّة