User blog comment:Lex wa Kaiho/What is Lumen Histoire?/@comment-90.202.79.252-20140820234927

My theory is Ivan called it Fairy Tails darkness because if the Magic Council found out they'd try to take it. Makarov stated that if the information Ivan had was leaked it would be the end to Fairy Tail. So it could be a spell that equals Etherion or if not far surpasses it, as we know mages are able to sense make (well most), Gildarts probably felt its immense magic got scared at what he thought it could do.

Secondly I think it could be the Tenrou Jade since Mavis in Fairy Tail Zero is trying to protect it.

Thirdly, it might actually be a Fairy or the remains of a dead Fairy which imits intense magic power, and there is a spell which is passed down from master to master in order to use the make or revive.

Forthly, same as my last one bit a Fairy could be a God and since Fairys have magic they taught human to use God Slayer Magic, which would explain allot.

5th, it's the reason why the Dragon Disappeared.

6th, it's the founders of Fairy Tail inside Fairy Sphere. Not much to back it up apart from we only know Mavis died and that she was buried on Tenrou Island. Also Fairy Sphere stops the flow of time inside of it. So the founders could be inside of it.