She hovered inches above the ground, screeching a noise that drove most beings mad. Behind her gathered others of her species, read to assist if their adversary advanced. The weight of her body compared to the size of her wings, meant that she couldn't fly too much higher than she was now. The genetic intent was to tower above her adversary, and it was enough to accomplish that.
As with many creatures that go back a long way in time, there is specialization. Members of a species that carry out special missions. There are caste systems among bees, where some are workers, other are drones, and they even have a queen. Ants take it even further by adding a fourth caste, which is the soldier. This large almost human looking creature was the fourth caste of the Faerie people.
How could the tiny Faeries create such a huge member of their species in comparison to the size of the rest, you may ask. How does nature accomplish size variations in any species? is the question to answer your question. Size variation by sex is common in many species, with the female being larger in some, the male in others. Birds seem to take that a step further by adding in the environment. Birds of the same species tend to be smaller where there is more competition for food. The Warrior Faerie is the size she is, because she had to be. The predator for the their species was the human, and they had to fight fire with fire.
The smaller Faeries were known to fly alongside or even ride arrows and spears to adjust their in flight trajectory towards their target. The little ones were know to fly close to the eyes of combatants, to give the Warrior Faerie an opening by distracting the adversary. Sometimes the small Faeries would tie something across the path of the enemy, so they would trip over it. But the killing blow had to come from a creature of similar size and strength.
The resources of a Faerie community to feed and arm a Warrior Faerie were so overwhelming that they were only bred in the most serious of circumstances. The sacrifices it took to create the chain of events to breed a warrior are greater than we could ever know. The time it took was even greater. The lack of resources has laid low many an army and species. Although the Warrior Faerie was a formidable foe, there were just too few to make a difference.
That is why the Faerie people exist no more.