Life Cycle of a Shadow

Editor’s Note: This story was published in the anthology A Compendium of Enigmatic Species, published by Practical Fantasists. You can find out how to purchase the full anthology here.
A shadow, it’s said, is patient—patient and invulnerable as death.
If the saying is true, that patience speaks to the fear that surrounds the mummy known in recent media reports as the Shadow Cocoon. But to recognize the source of this fear, one must first be familiar with shadows themselves, something few people truly understand.
Shadows: Kingdom, Phantasma; Scientific name, contested. A true shadow ought to be Umbra umbra, but some studies place the shadow cocoon in its own, closely related species, Umbra coccum.
Properly speaking, shadows are not those places where the light is blocked. In the earliest reconstructed languages, those places have no names, though the proto-word for shadow does exist. Shadows were the beings that lived in those places of blocked light. Through the corruption of time, they have lent their name to their native homes, been subsumed by them, been forgotten.
A true shadow, then, is born in the morning when the sun rises. The sudden light excites the particles of the air so they cast off a tiny essence of nightness. These essences clump together, drawn by a force similar to magnetism. When enough cluster, the nightness at the centre collapses into itself, forming a shadow heart. Or more accurately, a heart-brain, as this centre both pumps the shadow essence throughout its form and controls its movement, shadow-place to shadow-place.
Some mornings birth only a single shadow or even none. Other mornings, when the darkness is deepest and the sun’s rays most unexpected, dozens of shadows come to life. Throughout the day they move and shrink and find ways to hide from the cruel sun that sparked their lives. They grow leaf-like appendages to gather energy from whatever darkness they come across, and occasionally prey on those who stray too deeply into their realms.
As night approaches, they feel a growing power, and begin to tempt the edges of their safe homes. Those struck by sunlight wither, but some succeed in ensnaring other prey. Just as their power grows greatest, most of them die. A day is old age, and fortunately for the creatures of the light, they grow feeble even as their habitats grow to give them greater territory.
When the sun sets, the air draws nightness back into itself, stripping all life from the shadows.
From most of the shadows.
Some manage to plant themselves in the neck of a human host. Through the night they feed parasitically on their humans, and when morning comes, they grow dormant. Their hosts feel weak and unrested but otherwise well. The shadow finds itself immune to sunlight, but not exactly alive itself. It stays with its host in this dormant phase, sometimes for years.
As the phase ends, it covers itself in a cocoon of darkness. Few humans ever notice this cocoon, neither the hosts nor those who see them. But after a variable amount of time, the cocoon bursts, killing the host and sending a fully adult shadow out into the world. Safe from the sun and unconcerned with its old haunts, the greater shadow feeds on everything it can, skimming energy from light and darkness both from animals and plants, and from the flow of people and information throughout its environment.
Usually this adult phase lasts for only a year. Then, at last, it perishes, and seeds the air with new bits of nightness. The longest recorded adult phase was five years. This shadow was believed to have ushered thousands of people to their graves, not directly, but by shortening their lives, each by a day or a year.
Deep in the Andes, a mummy was discovered a century ago with the signs of having been a shadow host. Tiny fractures in the vertebrae show a distinct pattern, and the jaw is distorted in a particular, shadow-host way. This news excited those who study shadows, as it was by far the earliest known physical evidence left behind. Shortly after its discovery, a cocoon appeared on the mummy’s neck, surprising everyone. It was assumed that the shadow had already passed through this phase. Instead, the parasite remained, even after death, even after mummification. Nothing like this had been observed before. The experts anxiously awaited the greater shadow that would burst from such a cocoon, though most of the world remained in ignorance.
We are still waiting. Over the past week, rumours have leaked into the wider world of its existence, of our questions. The news reports are simplified but accurate as far as they go. The shadow cocoon has been discovered and is currently under close observation. By our best guesses, a one-hundred-year cocoon will likely mean that its greater form will live for at least a human generation, and millions will die early.
Opinions are split between two groups on what to hope for in regards to the Shadow Cocoon. Some wish it would come forth soon and end the waiting, before it grows so powerful that its final phase grows incomprehensibly longer and the devastation unbearable. They try to draw it from its cocoon, poking and pinching and harassing it until it may appear.
Others long for more time, trying to shield the mummy from those who would bother its current rest. Given time, they believe, we might discover a way to protect the world from its hunger, to fight back against night.
Wishes mean nothing to shadows, and thus far neither shielding nor harassing has caused the least reaction in the slumbering shadow, nor disturbed its deadly patience.