User blog comment:FairyRaven/Fairy Tail Chapter 386: Galaxia Blade, Review and Commentary/@comment-83.255.202.133-20140530164705/@comment-5268982-20140530175418

It certainly has something to do with Lumen Histoire, I agree. Maybe a certain requirement must be met for Mard's resurrection, like all Demons being defeated. That was my first thought anyway!