Must have equipment: Ribbon (the little creatures can inflict poison + confusion)
Optional equipment: Moogle charm (if you were to grind EXP)

If you have season pass, equip ragnarok sword, it is superb in warp strike.

https://www.reddit.com/r/FFXV/comments/5t367b/pitioss_ruins_revelations/

https://www.youtube.com/watch?v=HGwoRpqJlCs

Remember in the Omen trailer, King Regis mentioned: May the Gods forgive me, something like that.
What have he done to make him speak like that? Something forbidden? So blah blah blah, King Regis somehow learned to have this time control ability and he wanted to see his son(Noctis) and Lunafreya to live happily ever after(the end wedding scene).

In FFXV game, we/chocobros started by pushing the car but in the ending scene, where there is the REPEATED dialogue of the car pushing scene and Gladiolus said something like OMEN dialogue.

The time loop will keep on repeating till you get everything right (perhaps DLC, and you get to save Luna):
till you have the happy ending (the wedding scene).

lol I'm suck at summary. Welcome to discuss on his theory, better take a look at his video.

Quote from Tabata: Regarding the story aspects of the DLC, it will not just be about adding story that was not shown in the original game. We also plan to add different conclusions depending on how players play their game (Different results depending on choices made in gameplay). This is not meant to alter the original story in any way. We want to maintain that through DLC, players can also enjoy the game in other ways.