It's the semi-mystical belief that, through focusing, meditating, and harnessing your aura, you can create a being through mental effort alone. Imaginary friends on steroids. Ones that gain minds of their own and that others can see.

Chances are that the majority of so-called tulpas are hallucinations, but given the number of magical forces in the universe, especially with Homo Magi gathering on Sorcerer's World, there might be a basis in reality for some of the wilder claims.