Barely made it through... 9999 rusty dragons in seven or eight stacks.

This battle should be avoided; the author specifically made it so there are 9999 in 7 stacks so that the player would find an alternative path. :smile28:
And in general, the author's idea was to find all the parts of the Dragon Power and the Angel Alliance, and we are given hints to help us find each part of the assembled artifacts.

How did you get past the border guard, who requires the Angel Alliance? And where did you find the angel wings?

Added 2 minutes later

Of course, the battle is like a battle against superior enemy forces, but... the Evil Emperor has the "power of the father of dragons," which means you can't berserk, blind, or clone him, and then massively revive your army with archangels. That is, you can't win the battle without losses.

This is the final battle, so you can use everything.
If magic doesn't affect the enemy, you can use it on yourself.
For example, use 1 angel in a stack to retaliate against the devils, and then attack them with the main force.
And yes, Angels deal +50% additional damage to Devils, and vice versa.