User blog comment:FairyRaven/Fairy Tail Chapter 324: The One Who Closes The Door, Review and Commentary/@comment-5620199-20130322195507

My theory: The prediction that Carla had about Lucy singing and Mercurius burning is, actually, Lucy using an enhancement to close the Door and Mercurius being destroyed by the dragons, and I think Lucy was being possessed by Zeref to sing the song, because of what Mashima's ideas revealed to us: Something like Zeref telling Lucy to go on knees or something like this. :P Sorry for bad grammar.