The cause of the curse is Akheseram,or whatever his name is spelled. I think we should wait before making baseless theories. Anna could be Zeref and Natsu's mother. It's rather ironic,for someone who regretted his life,to thank his mother,if my intuition is right. Rather touching as well. Still,Zeref sure had a way with girls. Besides Natsu,his brother,he only thanked women.
Mashima really outdid himself here. I honestly don`t know what will happen anymore in this manga. i can imagine people getting pissed here,and others preparing to ditch the manga if Mashima can`t keep up this game. Not that I care.
Now that I think about it,we still don`t know the story of the celestial spirits,if they are artificial or not,and if so,who created them and for what. We don`t know what will happen when Lucy gathers all twelve keys,considering Mashima had Lucy refuse Libra and Pisces,I doubt it`s nothing. Maybe next chapter will give us some answers.
Well,considering Lucy looks just like Layla and they have the same VAs in the anime,both in the jap and eng dubs,I wouldn't be surprised if Layla "got around" her death somehow by using her own daughter as a vessel or something of the sort. It's the kind of stuff Mashima could easily pull of. We don't even know how Layla died.