In the Longest Thread Ever and Song's Omakes, a Seachi (also called an Eater-of-Souls) is a being that has two or more souls living within its body, each soul having the personality traits and physical form that it had in life.
How a Seachi is created
There are usually two methods for becoming a Seachi:
- Heritage. If at least one of the parents was him- or herself a Seachi, there is a chance that the child will be born a Seachi as well, with souls from each form the parents had.
- Ritual. There is a ritual that makes a willing sentient being a Seachi, but the ritual only bestows the gift on those who have no ulterior motives to becoming a Seachi (such as vanity, to show off, or to make crimes easier to commit). People who the Rite finds lacking are killed.
In some instances, there is a third method:
- Possession. If a pregnant mother or an egg is possessed by a ghost, there is a good chance the spirit will be entrapped inside the child, thus making the child a Seachi.
Abilities of Seachis
Seachis can shapeshift into any form that has a representation in the Seachi's soul (i.e. if he has a soul that had that form in life). With practice, a Seachi can also partially transform, allowing the Seachi to alter his body by adding onto (or removing from) it at its whim. Seachis can allow other souls to take over for the body while he tends to business in the psyche.
While the body is asleep, the Seachi retreats into its psyche, where it and its other souls have their own dwelling, called a Soul Room. A Seachi is able, while asleep, to interact with the souls in its body as if the souls and the Seachi were flesh-and-blood, from talking with them to playing a game with them to sexual contact.
If a Seachi makes bodily contact with another being while asleep, the soul of the creature the Seachi is touching enters the Seachi's psyche. This is only temporary, however, as the soul returns to its own body is bodily contact is lost or one of the parties wakes up. If both visitor and host are Seachis related by blood, then each side can send one soul over to the other side for a visit.
There have been reports of Seachis being able to swap bodies during full moons, but there is no hard evidence to confirm this.
Although Being a Seachi has adventages, it also has disadvantages.
While a Seachi is in control of the body, he can hear his souls talking amongst each other, and vice versa (the only exceptions to this are creatures immune to psionic abilities, who can only show telempathy).
Worse, a Seachi tends to be vulnerable to spells and items that would make it shapeshift. If subjected to such a spell, the strain on the body's molecular structure causes the souls to free themselves like water down a drain, causing the Seachi to spectacularly explode almost every time, destroying the body and the body's main soul. Seachis whose psyches are dictatorships tend not to have such things happen when subjected to such a spell, though their souls may rebel and (at the cost of one of the souls) supplant the Seachi and blow up, freeing every other soul within the Seachi. Mages have worked on a spell called Cloister to keep this from happening, but as its material component is a shard of Esteroth, it isn't a practical solution.