Illusion army

Mab whirled on her steed the moment the enemy broke, and lifted a hand. As she did, a cold wind descended upon Chicago from the north, the scent of it dry and sharp like at the beginning of proper autumn. It howled across the park, and the billowing vapors of mist and frost fled before it, sweeping the field clean of dust and smoke and mist, leaving the park suddenly clearly visible.
And I saw what Mab had really been up to.
As I watched, about fifty yards away, Mab led a cohort of Sidhe into a formation of octokongs, their weird arquebus weapons bellowing to little effect. A dozen yards beyond that, Mab led a cohort of Sidhe into a formation of dog-beasts and their handlers. Beyond them, maybe four or five more Mabs were hammering their way through several formations of those heavily armored ape-things.
And behind us, more Mabs were doing the same thing. The enemy screamed and fought. From one side of the battlefield, sorcery suddenly struck, with a sound like a thunderbolt and a spreading cloud of bilious green smoke that . . . just dissolved a pair of hapless octokongs that got in the way.
Glamour.
All of the other Mabs, all of the other cohorts of Sidhe, all the casualties inflicted upon the enemy by them—they were illusion. Figments of Mab’s imagination, given life by all the energy in the air.
I stared in awe. Producing an illusion is, honestly, a task that might be slightly more difficult, magically speaking, than actually creating the illusory effect for real. Every detail, every wrinkle in fabric, every stray hair, every blade of grass that bent beneath an illusory boot, every footfall, every exhalation, every faint scent—they all had to be held and wielded by the conscious thoughts of the source of the illusion.
Imagine one person running two thousand puppets at once.
Mab was doing that in the back of her mind, while hacking at the enemy with her frozen sword. She took stock of the battle and lowered her hand, and mist and haze once again fell like a curtain as the cold wind ceased.
Outnumbered dozens to one, Mab had pitted the sheer power of her mind against a supernatural legion—and she was winning.
As long as the enemy couldn’t find and target Mab herself among all the duplicates, we weren’t fighting an army: We were holding a narrow pass where only a single unit of the foe could see us in the haze and engage us at the same time. Chaos and confusion and terror filled the minds of her enemies, and from them she built a fortress where their numbers counted for nothing.
If left unchecked, Mab and her killers could destroy the entire enemy legion, one unit at a time.

Battle Ground Chapter 27, Page 250-252