Petals of the Seelie

When the first of the Fey flickered into life on Colossus they were of sunlight and twilight. Pure magic, creatures manifested of the sparks in between.
What the non Fey discovered was their spirits could be captured and used as an energy source. Once such peoples live in the Eye of Fairies, a jewelled city that harvests the Seelie, the Fey of sunlight.
To a visitor the city is one of glorious beauty and magical splendour. A utopia blessed by all. Magic and everyday life is merged, comfort is expected and egos massaged.
Farms are built on the north side of the city. Filled with flowers whose petals shimmer with every colour on the spectrum. The feed given to these flowers is made from the life force of the Seelie fey.
Ethereal pathways kept open by enchanted pillars are constantly travelled by the Gardeners. Armed with cold iron weapons and armour blessed to resist the charms of the sunlight realm the Gardeners hunt down the Seelie fey and bring them back to the farms.
As the magic of their life expires it is captured in nets made of cold iron wire. Bottled with specially prepared glass, usually protected with a sigil from one of the cities Wizards.
Back on the farm the life essence is scattered among the flowers. When they reach full bloom they are snipped and the petals taken to the Towers of Light at the centre of the city.
For obvious reasons the Seelie do not take lightly to being hunted for resource and many Gardeners have been slain and made examples of in the Sunlit Realm. Violent displays created by their corpses.
But the price of the Petals of the Seelie drives greedy people to chase dangerous things. The Eye of Faires always seeks more.