Soul strangler

The following documents consists of what could be recovered from a folder owned by Glowstick Bluebottom after their office burned. It is thought to be a dissertation written by a student on plant biology.

by Pouaseuille

"... And then, as everyone looked into the depth, they saw a dark silhouette. And they knew that the well was HAUNTED!!"
In a desperate attempt at being dramatic, our storyteller threw a bit of dry peat in the campfire, suddenly raising the flames. The audience was nonplussed. Disappointed, the young teller sat down in a hunch and proceeded to roast an apple on a stick.
"By the spirits, that's a tough crowd!" a deep voice rose from the dark. Everyone turned toward the source of that statement, a Pure Nomad sitting slightly further from the camp than everyone else. Even while sitting on a tree stump, they were towering over all of us.
"Think you can do better?" the storyteller asked defiantly. Though they tried not show it, they were intimidated by the presence.
The tall nomad leaned toward the fire. "Well, if you're inviting me. I know a story or two. Even lived a few myself. Let me think... Ever heard of the Soul Strangler?

— Extract from Campfire Stories an anonymous book gathering stories heard near a bardrel's moving pub.

Growing in some localized regions of the Middish Plains and the North of the Cylinder, the Soul Strangler is a both creeping and arboreal ivy known for its dangerosity for sapient lifeforms. The following essay gathers information on the plant, its symbiotes, and its cultural impact. Sources for this document include expedition reports from members of the Library as well as collected books unrelated to the Library itself.

Description

by Pouaseuille

by Pouaseuille

Soul stranglers are thought to be closely related to other fast growing vines. In particular, it shares multiple similarities with the invasive Frenzy Ivy. In the same fashion as the invasive ivies, soul stranglers have two leaf types. The primary leaves, also called juvenile or creeping leaves, are palmately lobed, and typically only pigmented on the side exposed to circle light. Leaf stems usually grow and rotate so that the leaves are correctly oriented.
Secondary leaves, also called adult or tree leaves, or even tea leaves, are unlobed, cordate, and usually thicker than the juvenile leaves. They only grow on the arboreal stems of the plant, during sexual reproduction. [...]
Soul strangler seeds are adapted to propagate through the air. After pollination, the pistil grows several thin hair-like structures, and dries out. The fruit, small and dry, can then be transported by the wind before being deposited in a new area.

Reproduction

Soul stranglers are known to reproduce both sexually and asexually. In a similar fashion to other fast growing ivies of the Cylinder, the plant's creeping vines are usually capable of vegetative propagation. Every stem can produce both leaves and roots, and separated fragments can usually turn into autonomous individuals. [...]
The plant's uncommon sexual reproduction pattern is the origin of its name. Unlike most plants, soul stranglers bloom is not triggered by seasonal or meteorological changes: it is triggered by the capture of sapient creatures. According to the professor-explorer Redthorn Slyrunnah in their book Plants of the north:

In fact, it is utterly fascinating. See, the plants won't flower if they reach a dead body. Not all living things work either: if you manage to drain an intelligent animal of all its Ghostpowder, and completely sever its connection to the consciousness flux, the blooming won't start either. However, if you manage to fully trap a spirit and a lot of ghostpowder in an object, and connect it to the global consciousness, you may manage to trigger a flowering!

by Pouaseuille

According to observations, the flowering doesn't start immediately after a plant reaches a host. The process starts over roughly a dozen of days.

While the vines remain creeping close to the ground, their growth pattern change when potential hosts stay nearby: some vines tend to grow around, and to separate from the ground. Some of these semi-arial vines produce small, hard and spiky roots.

As soon as a vine sticks itself around a suitable host, it starts a rapid growth spurt. Roots start to dig into the host's skin for stabilization, and vines start to twirl around the host.

As the plant surrounds its victim over a few days, it takes possession of the host's connection to the mental world. It also drains the victim's dormant ghostpowder, and repurposes them for its own growth. The victim slowly dessicates itself, and becomes a rigid trunk for the now quickly growing plant.

by Pouaseuille

In the case of a standing, human-size creature, it typically takes six to eight days for a stalk to reach the top of its host. As soon as it does so, the stalk starts to grow upward, and to divide into more stalks. This is when the flowering starts. Adult leaves are produced on the arboreal stalk, along with small inflorescences.

It has been noted that the arboreal forms of the plant typically last longer than one blooming. In addition, the flowering of one individual has been shown to trigger the flowering of other nearby trees. As a result, a "blooming wave" can propagate through an area that has been infested by Soul Stranglers for a while as a new host is captured.

Symbiosis

It seems obvious that the capture of an individual by the ivy would be very unlikely under normal conditions. Even if one gets a stalk stuck to their skin, they could relatively easily get rid of or cut the stalk. This is why, long before mental parasites were first understood, some phenomenon was thought to influence minds in the vicinity of Soul Strangler colonies.
As research on the subject evolved, it was recently demonstrated that in most cases, soul stranglers share a highly mutualistic relationship with a form of Brain gnats. The parasites typically slow down potential hosts, and even paralyze them as they get closer.
While brain gnats are a very diverse group of mental parasites, the ones symbiotic to Soul Stranglers tend to share similar characteristics. They also behave differently from regular folkloric gnats. Indeed, while mental parasites typically spread through the discussion of their existence between hosts, and gain power by slowly occupying an increasing amount of mental space of their hosts, brain gnats have access to another source of brainpower. It is currently thought that as the ivy grows around and dessicates its victim, the victim's mental capacities partly remain. Simply, they are entirely occupied by the brain gnat itself. As a result, while the host is functionally dead, the parasite's presence in the consciousness flux remains.
This is thought to be the reason why "Ivy gnats" are so powerful in the vicinity of soul stranglers, and the reason why they manage to completely parasite otherwise healthy hosts. As an individual previously infected by the gnat approaches a soul strangler colony, the fraction of their mind already occupied by the gnat acts as a weak point for a mental attack. The individual is incapable of defending themselves from the gnat, and gets quickly dominated.

Try to imagine the sensation. You feel compelled towards some place. You don't really understand why: perhaps you've heard some story in a nearby village, perhaps your lover died and you remembered a tale from your childhood. Whatever the reason, you've gotta go to the forest.
Then, as you get there, you trip on a stalk. Or two. Or perhaps you heard it was part of a spiritual trial to collect yourself on the vines, and that you'll be stronger if you ever get out of here. But as the vine coils itself around your feet and its roots dig into your skin you realize you won't.
A part of you, deep down, is starting to panic. The rest of you, though, doesn't. You feel numb. Slowly, as the roots dehydrate you, your body gets weaker. You think less about you, more about the vine. In fact, "you" starts to disappear. Your memories, your emotions... All gets erased as you become the vine.

— Extract from an report written in 5489 by Miller Herbalwack, a scholar shaman used to collaborating with the Library on spiritual topics.

by Pouaseuille

Uses and cultural presence

As a result of its mutualism with brain gnats, soul stranglers have an important presence in Middish culture. They are at the center of a wide array of local superstition, rural folk tales, and even urban legends. According to expeditions in Middish territory, both nomadic and sedentary groups are known to share stories about some local haunted forests, sad tales of lovers turned into plants, and myths of some ancient human-shaped tree guardians of the forests. All of those stories were confirmed to be brain gnats almost directly linked to a specific Soul Strangler colony.
While they are notably dangerous and require a decently protected mind to collect them, the plants also have some notable uses. Once dried, the arboreal leaves and fruits are used as an infusion, known for its bitter taste and its strengthening and slightly hallucigenic effects. As for the branches, they provide a high quality source material for ghostpowder-based enchantments. Indeed, the branches are already adapted for the internal circulation of ghostpowder. As such, they last notably longer before being altered by the corrosive substance. The preparation methods... [...]
Most of the end of the essay couldn't be recovered. Because the author student was not yet identified, it is unknown whether any copy of the full essay exists within the Library.