The answer, it turned out, was complicated.
Fate had already touched upon one of the reasons in his delirious, near-death state: tenacity.
Even as the humans' numbers dwindled, they continued fighting, not stopping even when they lost limbs or their comrades were sent flying. But the aesh shared this same tenacity, so it wasn't enough.
The other reason was ingenuity.
The aesh were no less intelligent than the average human, but they lacked the creativity of the humans.
As the aesh grew increasingly frustrated, its attacks became more vicious.
At the same time, it fell for more traps or tactics that the humans pulled out of thin air, until it was missing a hand and both horns, and its chest was dripping with blood from a gash that extended from shoulder to hip.
The last reason was perhaps the most important: superior equipment.
The aesh neglected armor, barring bracers, as they reveled in the thrill of battle, which they felt armor detracted from.
Sturdy steel could pierce their hides, but it wouldn't get very far on its own.
The humans couldn't pierce his hide with harmful enchantments, whose damage came mostly from expelled Mana, so the devastating arrow that killed the first aesh wouldn't do a thing against the demons' actual flesh, and neither would most poison Imprints.
But Fate's sword, which didn't have any Imprints that expelled Mana for attacks, could still be used, along with the standard Guard weapon.
These weapons were enchanted for durability and to prevent rust but didn't come with explosive attacks. A Guard would have to buy such weapons themselves.
If this wasn't true, Guards would have to rely on run-of-the-mill, unenchanted swords to kill demons, which would be harder to sustain in the long run as mortal weapons would chip and break with use.
Thanks to these Imprints, the Guards could block or deflect the giant, unenchanted mace with only minor wear and tear to their weapons, while the mace was dented every time it struck metal.
These weapons also were much sharper and sturdier than ordinary steel, allowing the Guards to do more meaningful damage.
The Guards wore armor as well, which was what saved the Guard that had been sent flying before Fate joined in the fight and allowed him to jump back into the fight.
It had been dented beyond repair and he had been forced to discard it, but he couldn't complain. He was still alive, after all.
There was also a fourth reason, one that wasn't true anymore: overwhelming power.
Humanity a hundred thousand years ago held a monopoly on Arch-Mages, or Tier IVs for Magical Beasts. Only dragons and other, more obscure Magical Beasts had Tier IVs of their own, but the demons had none.
Demons could take Mana of a higher Tier than them, but it more time than usual.
The double in Mana quality each Stage brought meant the demon wouldn't be properly equipped to break it down fast enough, so they couldn't escape harm from attacks levied against them by a Mage of a higher Level.
This power gap was one that few living things – beast, plant, demon, or human – could bridge effectively.
And since the aesh only had Tier IIIs at the highest back then, they were slaughtered like sheep whenever an Arch-Mage stepped up.
The demons had learned quickly to spread their attacks out so the Arch-Mages would be equally as spread thin, unable to attend each battle, which is where the first three reasons for human victory came into play.
The aesh dropped to his knees as his throat poured blood, the Mages stabbing him repeatedly with their swords and peppering him with arrows as Kravoss shot beam after beam.
Finally, the demon fell forward, his warped mace clattering to the ground as he landed on his face.
Fate sighed in relief as the monster dropped, the civilian Mages around him letting out a short cheer.
He glanced at the aesh with the sword, who Venden was currently battling against with other Mages.
Cait stood and let her injuries heal as Samantha consoled her Familiar.
Due to the gap between their power, and the demon's absurd strength, Gevum's abilities had only been able to slow the aesh's by a fraction of a hair. He had resorted to steering arrows toward the aesh's vitals instead halfway through.
The Kaleido cat, Pospo, sat tiredly around Cait's ankles.
Her scorching beams of light were Mana-based, unlike a Dracok's Breath. She could also heal from damage swiftly like her master, but that wasn't very helpful when the opponent could kill her with a misplaced kick, though this did remove the cut on her flank.
And her Mana absorption ability, a Blood Skill she shared with kitsubi and their succubi ancestors just like her healing, wasn't helpful either against an aesh, who relied purely on physical strength.
Only her ability to light up like a lightbulb whenever she wanted, a Blood Skill called Kaleidoscope, was of any use in the battle.
But since the night sky's darkness was replaced by the glowing red clouds overhead, providing a constant dusk level of light occasionally broken by the Light of the Empress' attacks, it was more of a distraction than anything else.
A distraction she presented whenever possible, running around to the humans' backs to distort their shadows and make their actions less obvious against their bright background whenever they were about to attack.
Running around like that was extremely tiresome, and now she wanted to nap. But she couldn't yet, so she kept her eyes open.
"It isn't over yet," reminded a Master Guard, who pointed his single-edged sword at the other two aesh within the walls, the one with the axe and the last one with a sword.
After a glance, he divided up the surviving eight Mages, including himself, to help with the other two battles.
Four would go to one, and four to the other. The Master Guard would take Samantha and two civilian Adepts to face the sword wielder, while Fate, Cait, a Guard Adept, and a civilian Master would take on the aesh with the axe.
"Your Familiar should even it out," the Guard explained to Fate. "Dracok Breath is one of the few magical things that can hurt the demons more than they can take from the Mana powering them.
"I doubt a Tier I beast can get deep into the aesh's skin, so have him aim for the eyes and attack the joints to disrupt the demon's swings."