That's a lot of 'em...
An artifact of phantasmal power, the Banner of the False Legion attunes to armies under its leaders command and creates illusionary doubles of every soldier. There's a theoretical limit to how many doubles it can created, based on both the force's cohesion and loyalty, and the generals confidence in his forces. The lie, as always, favors the bold.
The Banner is a burgundy-red tapestry of shifting motif, changing as its owner does. The sign of the leader is always emblazoned upon the center, usually crossed with two swords. If the leader has no particular sign or crest to call his own, the banner will instead show the mark of its creator - an ouboros circle, ridged with broken blades.
Attuning the Banner to a standing force requires every warrior to touch the banner while it is held by its owner. After that, the general need only raise the banner - either himself or by order - to manifest its power. Each shade crated by the Banner is a wispy, insubstantial thing, mimicking the soldier who's touch imparted it with essence. From distance, they're almost indistinguishable from another warrior among the press of bodies. Closer, the deception becomes apparent, though most are still distracted by phantom strikes or sudden, startling lunges by the fake warriors.
The Banner's illusion loses cohesion as formations do. When soldiers scatter or begin to flee, the shades drift wider apart and become like mist. Even if the soldiers rally, their phantoms never again rejoin the fray as they once had.
The illusion lasts for hours if uncontested, longer still if the general owning the banner can imbue it with his own energy. If the Banner is ever lost, falls to the ground, or taken by the enemy, the shades it has created evaporate like shadows before the rising sun - usually followed by a route by soldiers who found courage in their illusionary numbers. Likewise, any damage will cause a shadow to dissipate, and no matter how armored they may seem, they are as flimsy as any other lie.
Cleaver generals use the banner not in the battlefield, but to create deception elsewhere. A small marauding force can give the appearance of a vast army, or a siege drowned in hopelessness by an seeming endless army outside the walls.
Much to the chargin of some, only one banner work at one force of soldiers at a time. Those fortunate enough to own several usually distribute them among sub-commanders, giving each company the appearance of many, and with much less logistics attuning the Banner.
A warrior's attunement to the Banner lasts as long as his or her inclusion in the battle-ready force does. Traitors and villains remain attuned, until they make their move or desert their posts.
Using the Banner isn't without its risks. More than one commander have had their confidence bolstered by seeing numbers that weren't there, forgetting that they only have half of what they can see.