Final Fantasy 14's patch 6.4 trailer reveals the path we'll take to the Dark Throne

pcgamer.com:

Final Fantasy 14: Endwalker has suffered from some update droughts lately—we've received a lot of fun tasks to do, but they've all been short-lived. Variant Dungeons and Island Sanctuary have tried to fill the gap left by exploration zones, but they're unfortunately one-and-done experiences.

Thankfully, patch 6.4's trailer is utterly loaded with story hints to whet my cutscene–starved appetite. I'm here to pass my theories onto you, so if you haven't watched the trailer yet, now's the time(opens in new tab). 

Before we get started, I'd like to mention that I'll only be covering information regarding the Main Scenario Quest, otherwise we'd be here all day. 

The trailer opens with Golbez—our big bad for this patch cycle—stood atop the Thirteenth's red moon, beseeching someone to join him. His objective? To fully invade the Source, where his immortality-cursed subjects can finally die a true death.

While this seems like a plea to the player at first, it's followed up by a demand to «feast upon this dragon, and its ardent longing for home with it». «This dragon» refers to Azdaja, who he's been keeping captive in the void for centuries. 

We know the Archfiends we've been slaying grew strong because they'd devoured Azdaja's aether, so my gil's on Golbez raising an army through similar methods, one that shares Azdaja's burning desire to return to the Source. We also see Vrtra reuniting with Azdaja, though what mental state she'll be in after centuries in the Void is anyone's guess.

The trailer shows us hints as to how we'll return to the Thirteenth after our previous portal was destroyed in patch 6.3. Zodiark's former lunar prison swells with energy, followed by a scene of us flying through the rift between worlds upon Vrtra's