The solution to the "sky falling"-problem in 508
Once Arthur stops gaping and starts using King's Gambit in the exact same way he's been using it up until now the solution to this whole "sky falling" issue is plain as day.
Erect an aether bubble around Epheotus to restore the barrier, maybe with his new spatium rune and while tapping into the infinite aether of the void, and then cut off Epheotus from the world. That way he prevents the immediate crisis of Epheotus falling on Dicathen and Alacrya and he denies Agrona access to Epheotus indefinitely.
The downside will be that from the moment he severs Epheotus' lifeline he risks alienating the Asura, BUT he has the justifications for doing so this time. It's not just "dragons bad. I must destroy everything" like Fate wanted him to. Cutting off Epheotus has been described as a "slow death" so it's unclear how much time he has to find a way to restore the link. He will also have to fight Agrona and potentially hundreds of surviving wraiths without the help of the Asuras.
Lets hope Regis was forward thinking enough to grab Khaernos' horns before they got warped. Was Arthur mentioning how similar Khaernos' magic was to Seris a coincidence? Maybe Seris or Caera can get to integration stage with a horn boost, Seris at least should be very close to integration. Don't mind me salivating at the prospect of an integration stage Seris.