User blog comment:IamJakuhoRaikoben/Chapter 443: And Then, The Land Was No More, Review./@comment-81.82.57.70-20150710163801

I just had an idea:

What if Lumen Histoire is another Demon created by zeref?

Zeref preserved the body of natsu to create END, so he may have done the same to Mavis, who might have been his love interest.

If Mavis' corpse was turned into a Demon after her death, it might explain why some call it "darkness" or refer to Lumen as a weapon. Zeref wants his Demons to be strong so they can kill him and perhaps he made her as a "back-up" since Natsu may have already been snatched away by Igneel at the moment of Mavis' death.

Mavis' body is also naked, just like Minerva, Mirajane and Natsu when they underwent Demonification. If her "human" body was preserved for whatever reason by someone else than Zeref, you'd think they at least put some clothes on her.

Maybe Ivan will return in the current arc and perhaps it was the Albareth who told him about LH. Albareth may have opted for someone with inside-information to seek LH, as this would seem less suspicious to the Council, thus reduce the chances of getting another Etherion down their throats.