User blog comment:FairyRaven/Fairy Tail Chapter 301: The Dragon King, Review and Commentary/@comment-5268982-20120930091853

Maybe someone can connect all those events with each other, so I'll type then down chronologically:

Now if one can connect all those points(besides Mashima) between them...
 * Dragons have war with other Dragons and Dragon Slayers, and a man is turned into a Dragon by using Dragon Slaying techniques (I don't believe Arcadios, Zeref did not change Acnologia to a Dragon, because Natsu, Cobra, Sting e.t.c also become Dragons partially when using Dragon Slaying techniques).
 * Porlyusica somehow comes to Earth Land and communicates with her counterpart.
 * x777: Dragons disappear, Layla Heartfilia dies.
 * Exceeds join Earth Land (it's not a filler arc for god's sake, it has to be important. Maybe it's connected to the Porlyusica event).
 * Zeref awakens.
 * Acnologia arrives and eradicates Fairy Tail. A new age begins according to Zeref.
 * x784: Fairy Tail returns, Grand Magic Games begin.
 * Dragon King Festival underway, Arcadios and Mystery Woman appear, Zeref is hinted to be around too.