A Tulpa is essentially a psychic construct imbued with aspects of what Jung called 'The Anima/Animus', as well as the Shadow, the Muse, and additionally of what we often call 'Guardian Angels'.

They are likely conscious, thinking, and reasoning (a secondary 'I'), and may represent an inter-dimensional linkage between entities; but that is just supposition.

I suspect that Tulpas are capable of bringing the brain under a deeper level of control than the primary consciousness, the latter ultimately acting as the final gateway between psyche and expression.