How do I use Armageddon's Blade?

Why is it necessary to have only one stack? Simply put, when we are significantly weaker than the enemy hero in terms of army strength, it is more advantageous to use Armageddon to destroy both our own and the enemy's creatures (at least, part of them). Either way, they are destined for the same fate, but they can carry less with them. Alternatively, this is a way to end the battle, even if the situation is not in our favor; Armageddon decides. Sinister in a duel is a perfect example. Ending the battle with Armageddon in many tournaments is even counted as a "draw," but not as a victory for the Dark Elf.