The Soul in the world of Soul Eater is regarded as an individual's own spiritual essence and/or immaterial part of their being and is one of the most important, if not the most important, concepts within the series.
It is the origin of all the characters and is a manifestation of each character's personality, psyche and abilities. People with special types of soul can utilize different powers and abilities. Souls can come in many different variations, differing in type and strength. Souls are important in the DWMA, as Meisters can only wield Weapons that are compatible with each other's souls.
Main Article: Soul Resonance
The true power of a Weapon and Meister can be exerted by them resonating their souls together, a Soul Resonance. The meister's own wavelength is very faint in energy but when a meister holds a weapon, the soul wavelength is amplified, giving it lots of power.
Main Article: Soul Wavelength
Each soul gives out a "soul signal", in which is connected to what is called a Soul Wavelength. Each soul has its own Wavelength of a particular frequency. Soul Wavelengths vary in strengths and frequencies, depending on how strong and big the soul is, and also on the health of the person concerned. Individuals who have large souls have a powerful Wavelength.
In Soul Eater, it is possible to consume souls. The only known entities in Soul Eater able to consume souls, however, are Demon Weapon. However, it is possible for a meister, should a method of combining them with a demon weapon permanently, to be able to consume souls via resonating. 
Though individuals in the Soul Eater anime have been seen able to consume souls, this is an inconsistency and is, more or less, followed within the future episodes.
All souls, however different they are in appearance, all share the same basic shape: a round ball about the size of a grapefruit with a flame-like tail, similar to the Hitodama depicted in ancient Japanese myth. Each person's soul differs in appearance, color, size, strength, the strength of the Soul Wavelength etc. However, the average human soul appears to have a light blue pigment when isolated from the body, as well as a lack of distinguishable features.
Inside a Soul
As well as containing a person's thoughts, emotions and personality, a soul in the Soul Eater series also seems to contain a sort of spiritual dimension within itself. These spiritual dimensions seems to reflect the person's personality. For example, Soul Evans's spiritual dimension is The Black Room, a dark room with a red and black checkered floor with red curtains, a record player, and a piano surrounded by tall eye-shaped candlewicks with blue flames. This reflects his sarcastic twisted personality, as well as his affiliation to music and it also takes in the insanity from the Black Blood into account as well. In their soul's spiritual dimension, the owner of the soul resides inside it as a sort of spiritual avatar. Both the physical person and this avatar seem to be linked and of one and the same. The avatar in the spiritual dimension takes on a certain appearance and wears a certain attire, to match the environment around it. So Soul Eater Evans in his Black Room wears a black pin-striped suit with a red dress shirt and tie. However, especially in the anime, the avatar's appearance sometimes changes, and is sometimes the same as the person in physical form. Crona's original spiritual dimension is described by Maka as being, "very dry, like a beach with no ocean". Crona's avatar is him/herself as a child.
When someone resonates with the person, their avatar can enter the other person's spiritual dimension. In doing so, their appearance and their attire also changes to match the spiritual dimension of the person they are resonating with. When Maka enters The Black Room, she wears a black dress, and her attire matches with Soul's in terms of atmosphere and formality. When she entered Crona's spiritual dimension, she became herself as a child.
It is possible for a separate entity, such as Little Ogre and Masamune to exist in a person's spiritual dimension. Also, depending on the person's situation, mental state etc. the spiritual dimension is shown to alter in appearance from time to time, although almost always reverting back to normal.
- Monster Cat Soul
- Bloodsucker Soul
- Human Soul
- Demon Weapon Soul
- Witch Soul
- Werewolf Soul
- Shinigami Soul
- ↑ Soul Eater Manga: Chapter 2
- ↑ 2.0 2.1 Soul Eater Manga:Chapter 16
- ↑ 3.0 3.1 Soul Eater Anime: Episode 19