The time between Diablo's declaration of war and the end of Hades' attack on Dodekapolis was less than an hour.
And yet, there were already devils knocking on Olympus' doorstep before the universe could even recover from the loss of 4 Main Entities, 2 of whom governed the critically important Aspect of War.
How were there devils already at Olympus less than an hour after Diablo's declaration?
The answer was exceedingly simple, but complex all the same.
The first thing that should be noted was that Diablo's declaration of war had been recorded by Diablo himself.
This recording was then distributed to the dozens of universes allied with the Hell Universe's Devildom.
As for the means of travel, it was naturally the drifters working under Larry who had brought Diablo and Creusery to Olympus, making use of the trip that Arthur had passed on to Diablo.
