Nystylvrn (nih-sTIHLL-vern)

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Star Terrors. Bloodrays. Night Swarmers. The Winter Scourge. The Hunger of the Dark.

Nystylvrn are a species of rky ray that swarm in huge numbers and prey upon large mammals. They are active only during Dusk years on the northern edge of the Sanori grasslands. They can fly completely silently, turn almost invisible in the dark, and can strip a horse to the bone in an hour.

Basic Information


Nystylvrn are about a foot long and weigh around four pounds when their stomachs are empty. They are capable of consuming enough meat to double their body weight in a single feeding.

They have short, angled sails that taper to razor-thin edges. Their sails tear often but heal quickly, so they are often seen with many nicks and scars. Their sails are optimized for speed. Nysylvrn can tuck their sails into their teardrop-shaped bodies and dive at frightening velocities.

They have small mouths lined with pointy, serrated teeth designed to strip flesh from bone. Their bite strength as individuals is not particularly powerful, and they are only capable of biting away tiny bits of meat at a time. In numbers, however, this quickly becomes deadly. They have a second row of teeth tucked behind the first, which will move forward to replace any teeth that are lost.

Placeholder Image by Aster Blackwell

Perception & Sensory Capabilities

Their eyes are large and placed on either side of their head. They have near 360-degree vision. They can see distant objects quite well but are near-sighted. Their eyes can detect wavelengths on the infrared spectrum, which allows them to easily spot warm bodies, even in the dark. They rely on their spacial awareness to navigate around objects that are close to them. They also have an advanced sense of smell, which they use to track potential prey, navigate to their home perch, and identify individuals within their swarm.

Genetics and Reproduction

Placeholder Image by Aster Blackwell

Nystylvrn reproduce sexually and mate at the beginning of spring. After mating, the swarm will fly into the forest. Females lay their eggs underneath the bark of fir trees. They lay up to a hundred eggs, each no bigger than a quarter of an inch in diameter.

After the eggs are laid, the Nystylvrn swarm will continue to hunt nightly until the daytime grows long enough that they can no longer fly. Stranded on the ground, they become food for terrestrial predators.

Nystylvrn eggs remain dormant until the end of the Dawn year, when they begin consuming their yolk and growing. By the beginning of the Dusk year, the surviving eggs will have swollen to nearly six inches in diameter. At this point, they can be spotted from the ground as round, blue growths crowding the upper branches of fir trees. Sometimes there are enough eggs on one branch to cause it to break. The fallen eggs quickly become food for scavengers.

It is not known exactly how the eggs sync up, but on a bright night at the beginning of the Dusk year, every egg on the same tree will hatch at once into a juvenile Nystylvrn. They immediately take flight in search of their first meal. Once they've digested their first kill, they will have matured into adults. Swarms typically consist of at least fifty individuals.

Ecology and Habitats

Nystylvrn spend their nights patrolling the moonlit skies of the Sanori grasslands. They prefer these hunting grounds, as the wide open space makes it difficult for their prey to hide.

When the suns begin to rise, the swarm retreats into the forest, where they will perch amongst the trees. They are careful to spread out their numbers so that they cannot be easily detected. Nystylvrn rest during the day and awaken at night to continue their hunt.

Dietary Needs and Habits

Nystylvrn are strict carnivores. Their diet consists of 100% raw meat. They do not need to feed every night. Average sized swarms remain satiated for up to two weeks after a good meal. The Nystylvrn will stay perched in their trees for several nights after eating to allow themselves to digest. Their waste products are very beneficial as fertilizer for the trees that they rest in.

Nystylvrn prefer large mammals like gemsteeds and placeholder as prey. They don't often attack people when they are alone. Nystylvrn are attracted to sources of heat, so it is advised to wear well-insulated clothing and avoid lighting fires while travelling in Nystylvrn territory.


Nystylvrn are not very intelligent and don't know much else besides hunger and violence. They spend their short lives soaring from meal to meal and tree to tree. Despite the myths, they are not capable of grudges, do not remember faces, and do not have any moral reasoning as to who they attack.

They are not completely stupid, however. They can be fooled temporarily by various tricks, but the same trick will not work as well on the same swarm the second time. They rotate between patches of forest to avoid predation, and they are keen enough to notice if their favorite perch has been compromised. They are also aware of when they have bitten off more than they can chew, and will retreat if they encounter too tough of a fight.

Genetic Ancestor(s)
1 year
Average Weight
Average Length
Body Tint, Colouring and Marking
Dark navy blue to black skin. When they are soaring, they glow a faint blue. When they dive, their glow extinguishes and they turn near-invisible in the darkness. Their eyes glow brightly when they attack, giving them the appearance of a swarm of angry stars.
Geographic Distribution
Facial Characteristics & Features
Small mouths lined with sharp teeth, wide circular eyes with silvery irises and slit pupils
Symbiotic & Parasitic Species
Nystylvrn have both a mutualistic and parasitic relationship with the trees that they sleep and nest in. During the Dusk year, the relationship is beneficial to both, as the Nystylvrn gain a safe place to sleep and the trees get fertilized from their waste. During the Dawn year, however, Nystylvrn eggs can be harmful to the tree's protective bark, rendering the tree more vulnerable to the elements and other parasites.

Cover image: SanZera world cover by Aster Blackwell


Please Login in order to comment!
Feb 20, 2023 15:37

Piranhas with wings ARE worse than normal piranhas, it seems.

Feb 20, 2023 23:50 by Aster Blackwell

At least they're only around every other year!

Feb 28, 2023 17:56 by Dr Emily Vair-Turnbull

'Their eyes glow brightly when they attack, giving them the appearance of a swarm of angry stars.'   I love this imagery so much. :)

Mar 1, 2023 02:49 by Aster Blackwell

aaa thank you!!