The troops from the four empires had been watching the fight between the Dullahans and the Elemental Death Knights as well, but they didn't remain idle once the demons started moving.
Though they did wait for the demons to move first just so they could catch the demons off guard.
Catching the demons off guard like this allowed them to rain their attacks down on the demons like this.
That stopped the demons from approaching the undead to help.
The demons only staggered for a few seconds before trying to push towards the Dullahans and Death Knights again.
All that did was result in them being bombarded by another wave of attacks from the four empires.
It seemed that the four empires did not want to allow the demons to get anywhere near the Dullahans and the Death Knights. Of course, that only made sense since allowing them to rescue them would mean allowing them to save a powerful enemy.