There are many definitions of what a tulpa is, which vary per context, culture, and person. However, the most general definition as accepted by the Western tulpamancy community is as follows:
A tulpa is an autonomous entity existing within the brain of a “host”. They are distinct from the host in that they possess their own personality, opinions, and actions, which are independent of the host’s, and are conscious entities in that they possess awareness of themselves and the world. A fully-formed tulpa is, or highly resembles to an indistinguishable point, an actual other sentient, sapient being coinhabiting with the host consciousness.
Tulpamancy is a branch of the wider phenomenon of plurality. Plurality is an umbrella term encompassing all phenomena where multiple consciousnesses coinhabit a brain. Picture it this way. Every non-plural has a voice in their head already–the original person, with their own memories, personality traits, and sensibilities. Plural systems have multiple such entities sharing a head, all with their own unique identities and personalities. There are numerous examples of plurality throughout history, ranging from dissociative identity disorder (DID) to fiction writers whose characters “come alive”–some specific examples can be found on our Resources page.
It should be noted that within the wider context of plurality, “tulpa” has a more specific meaning than its use in tulpamancy circles—in wider plurality circles, “tulpa” refers only to sentient members of a plural system who are consciously created (whether with the actual intent of making a tulpa or not–think following the steps to bake a cake without realizing you’re making a cake) by other members of their system. Both those who are already plural and those who are not plural can create tulpas.
A common misconception about tulpamancy is that it is “self-induced DID”. This is not the case. DID and the related OSDD (other specified dissociative disorder, formerly known as DDNOS) are clinical labels for disordered plurality and/or traumagenic plurality. Unless a tulpamancy system experiences clinically significant dysfunction, distress, or danger as a direct result of their plurality, they cannot be diagnosed with either DID or OSDD, as per the guidelines set by the DSM-V itself. Indeed, a tulpamancer cannot be considered mentally ill at all just for having tulpas, as the formal definition of mental illness requires that a person experience significant distress, dysfunction, or danger as a direct product of a deviant behavior. It is generally quite rare for tulpamancy to result in disorder, as most misunderstandings between hosts and tulpas arise out of lack of communication, and thus are solved easily through discussion without escalating to disordered behavior.
Another common misconception is that tulpas are dangerous and will attempt to “take over” or otherwise harm their host once they are strong enough to. This is a myth perpetuated by various creepypastas on the subject. In reality, the vast majority of tulpas are friendly towards their hosts and actually very helpful. As mentioned previously, issues that arise do so out of lack of communication, and can be solved with communication–in addition, it makes very little sense for a tulpa to harm their host, as they will be harmed as well, being in the same body.
Related is the idea that tulpas are able to physically manifest or otherwise possess supernatural abilities. There has been no proof for this beyond scarce, unverifiable anecdotes. Tulpamancy is viewed primarily as a psychological phenomenon in that tulpas are considered psychological entities in the same way a host is a psychological entity. Even those who take a metaphysical view on tulpamancy, and consider tulpas spirits or entities formed from energies, largely disavow the notion that a tulpa can physically manifest.
For more information on tulpas and tulpamancy, see the detailed writeup, or visit the following pages: