A little story I cooked up based on a few visual inspirations from Cult of The Lamb! Some aspects are the same, but I have a take on it that I enjoy personally. I hope you enjoy.

Much thanks to a  Fordoxia for some proofreading help!

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Famine is an ever-present danger within this world. Many a community relies on any method they can in order to prevent hunger from wasting away their populace, often sending their members into the dangerous wilderness in search of food, often with disastrous results. The forests are full of dangerous creatures that few are able to fend off in their search for berries or other sources of sustenance. Fertilizer is not so difficult to come by, but seeds are, and getting the seeds back often proves difficult.

It is a point of common knowledge that life energy given to the earth would cause crops to grow faster, with more seeds to ensure future harvests. As animals and people alike are full of such life energy, one dubious strategy for ensuring better plant growth is to sacrifice said animals, or even people, and allowing their energy to pour into the earth, preventing famine from harming the other members of their community. In desperate times people are occasionally sacrificed in this manner, though naturally this is not a desirable practice.

A solution for overcoming such hard times was reached in at least one community, one that have taken to a particular kind of doctrine. Their discovery in the wilds is one of great interest; mushrooms. These ones are of particular size, and some grow to rival even the trees that normally give them shade.

Whilst the tale of how their hidden powers were discovered has been lost to time, the community that discovered these curious mushrooms have something that gives them the help they need in providing life energy to the soil, ensuring bountiful harvests season after season. This sect soon became known as the Spore Keepers. Taking on a fanaticism that soon spread to other desperate communities, the Spore Keepers found a different way to sacrifice their devoted in order to ensure the health and bounty of their harvests: once a follower among the Spore Keepers is ready to devote their body to the task of maintain the health of the crops with their very life, the other Keepers bind them to a sufficiently mature specimen of mushroom.

These mushrooms (now known as Harvest Caps) form a particular symbiotic relationship with those who stay too close to them, for better or for worse for the one involved. Over time, the flesh of the fungus will slowly grow over a living creature, eventually making that creature’s soul bind to the fungus; the flesh of both mushroom and creature merge and become one. There are instances of the flesh merely growing over a creature and supporting them in a similar manner; in this instance, a creature can be freed with enough effort. Without runic magic to manipulate the Harvest Cap to interact in this way, such cases are rare.

Once the process of merging is complete, the person will become a somewhat recognizable shape along the trunk. Hollow impressions of their eyes and mouth remain visible and are still able to freely express. At this stage, there is nothing that can separate the Harvest Cap from their new partner. Excess life energy generated by the creature is used by the Harvest Cap to not only to grow in size, but is also distributed steadily among the nearby soil, causing plant life to flourish under conditions that would normally be inhospitable.

Such a change for the joined creature gives them some interesting abilities aside from the invaluable aspect of providing the land with life energy. Beings that have merged with a Harvest Cap, referred to as "Growths", exhibit limited telepathic and telekinetic power. While the range is quite limited, it is enough for them to communicate with those willing to come close to the Harvest Cap and listen mentally. With enough effort, Growths are able to levitate objects and even people. Such telekinetic power is useful, as Harvest Caps will grow and become able to accommodate new Growths provided in further sacrifices, the next sacrifices able to be lifted up and held close by the Growths’ telekinetic powers.
Growths do not need to eat, nor do they require sleep, although they are able to will themselves into a state of hibernation for short or long durations. When interviewed on the topic of this hibernation state, almost all Growths report the ability to lucidly dream to the highest capacity possible, with the ability to share a dream with other Growths that occupy space upon the same Harvest Cap, or even within nearby Harvest Caps.

Thanks to their powers, Growths are still capable of being active members of the community, even as clusters inside their respective mushrooms. Harvest Caps with many Growths are often referred to as Harvest Totems, featuring many faces among the fungal flesh of the Harvest Cap, which exhibit enough telekinetic power to plant crops, harvest produce, and manipulate tools in order to handle farming all on their own. Entire communities that follow the doctrine of the Spore Keepers are fed almost entirely on the work of the Harvest Totems, working alongside them to ensure bountiful quantities of food for all.

When interviewed, Growths often report feeling of comfort and belonging among their fellow Growths and the Harvest Cap itself. It appears that even though feelings of fear or anxiety are common enough to set some back initially, most Growths become calm and even quite happy after some time of being part of a Harvest Totem. The reasoning among many was simple enough, reporting constant feelings of comfort, lethargy, and satiety, as well as a solidarity with existing Growths.

With the Growths themselves reporting a high rate of happiness and the communities utilizing the Harvest Caps to such a great effect, these Harvest Totems are undeniable evidence of the Spore Keepers’ effective doctrines, causing their faith to spread, much like the spores of the giant life-giving mushrooms themselves.