A deadly, parasitic plant, the soul tree exists in two dimensions simultaneously and infects people in their sleep.
Soul trees are not a well documented species, as the deaths they cause are difficult to attribute to them. Many cases of people dying in their sleep are speculated to be caused by soul trees, but once the host has died there is no way to confirm. They are primarily documented in recent studies of the metaphysical plane, which does not account for many tales or legends.
Soul trees start as a small seed, about the size of an apple seed. The seeds exist in two planes of existence; the real, waking world, and the astral plane. The astral plane can be accessed in a wide number of ways, including some drugs and meditations, but is primarily accessed via dreams. While the seeds do exist in two places, they will only sprout and begin to grow if they are consumed by a human (or other intelligent species) while in the astral plane.
To accomplish this, they will appear as a wide variety of fruits in the astral plane, to entice dreamers and travelers to eat them. The seeds in the physical world are housed in bitter, poisonous fruits, and so fall from the tree largely untouched by anything. They will sit dormant unless the astral version of the seed successfully begins to grow.
The seeds will take time to grow, aided by both the physical nutrients of the body they reside in, as well as the continued access to the astral plane. People who only reach this place during sleep may never produce enough energy for the seed to sprout, but continued travel there will allow the plant to grow faster. If the seed successfully becomes a sprout, it moves to the next phase of its lifecycle.
As a sprout, the soul tree directly feeds on their host. In the physical plane, the sprout grows and appears normal, with smooth grey bark and small, rounded leaves with a single point. They are often mistaken for apple trees, and some have even been grown intentionally by people who aren’t aware of their origin. The fruit will not grow until they reach several years of age.
In the astral plane, the roots begin to spread through the dreamers’ form, widely regarded as the soul, starting on the inside of the body before making their way to the outside from any number of openings. As this body is not technically physical, the soul can continue to move around and have no issues for a long period of time, allowing the sprout to continue feeding and growing.
Eventually, the sprout will either grow too large for the soul to continue moving, or will overtake the soul’s ability to continue feeding it without issue. At that point the soul becomes immobile, stopping where it is on the astral plane as the soul tree roots spread past the body itself to the ground. In the real world, the sprout, now a proper sapling, will possibly start growing fruit.
The soul, unable to continue moving or returning to the body, will cause the person to sink into an immobile sleep resembling a coma, and cannot be woken up. They will eventually die, but the tree, with its’ roots now established in the ground in the astral plane, will continue to feed on the body until it is completely consumed. The persons face is often still visible in the bark in either form of the tree, the only obvious sign of the soul tree’s existence.
The tree, once it has killed its’ initial host, can live up to 100 years. The physical tree does not need to be anywhere near the host person.
Both the spiritual tree and the real one are tied together, and the death of one will be the death of the other.
The part of the tree in the physical realm is as vulnerable as any plant, and if it is killed the parasitic branch in the infected soul will also die. If caught early enough, the host will survive and recover, though they may carry long term symptoms of fatigue and insomnia. The sprout in the astral plane cannot be physically harmed until it makes its’ way out of the body, but at that point is far harder to remove without killing the host.
The issue is the finding of the sprout, as it can be anywhere in the world. In order to find the tree, one needs to find the sprout within the astral realm, which can be used to track down the physical one. The full process requires a complex tracking spell, so is better left in the hands of an expert.
To confirm if a person has been infected, the easiest way is to check their breath while they are in the astral plane. While their spirit is there, their breath in the real world will smell of rotting fruit, and they will be lethargic and more tired every time they sleep long enough to dream.