Imposition

Imposition is the act of perceiving a tulpa in the physical world with your body senses. It is considered to be a voluntary hallucination that can then be controlled by a headmate. Since it is simply a hallucination, the tulpa is only perceptible by the body that they exist in, and not any other third parties. Imposition is generally mentioned in reference to visual sight hallucination, however with practice all 5 senses can be hallucinated.