Fairy Tail Vol. 43 (manga)

The demons of Tartaros are murdering Council members to try to get to a secret weapon with the power to wipe out all who would oppose them in one fell swoop. But what is this weapon? How could killing ex-Council members help them get it? And how do they even know about it in the first place? Natsu and his friends need to solve these mysteries if they hope to stand up to the demons!