A physical materialization of a thought, resulting in the creation of a being or object.
A tulpa is the given name to anything formed through the meditation (focusing) of an idea. The theory is that if you meditate hard enough on an idea, it will materialize. Tibetan monks practice this often, and teach it as part of their learning. Tulpa do not have to be live-creatures but can also be inanimate objects, animals, furniture, or creatures. There is a theory that the entire universe was made through tulpa meditation.
A tulpa is hard to define, as anything could possibly be a tulpa. While the idea is still being focused on, the object or creature may change & morph into different forms as the idea itself changes. Tulpa can only be destroyed by eliminating the thought (if the tulpa is not yet formed properly), or the diluting the concentration of the though, then destroying the object or creature.
Interestingly, Mordechai appeared to fit standard Chaos Magick practice for accidental creation of a 'Servitor' from a Sigil, and appeared to be working its way up to an 'Egregore' (see: The Fluid Continuum)