Doesn't it seem like the human brain is somehow programmed to create these sorts of things? From Native American spirit animals, to my own personal Jesus, to the imaginary friends who most children create, to AndA's tulpas, it seems like we have some sort of need to seek strength or advise or guidance from something outside of ourselves.
When my daughter was about 3, when I corrected her for making her "5"'s backwards, or when I suggested that she could build a block tower higher when it had a larger base, she would sometimes dismiss my suggestions, and explain that "cousin Lilly' had told her to do it the way she was doing it. "Cousin Lilly" told her to do a lot of things. Of course, we don't have a cousin Lilly.
Jesus gives personal advise to lots of Christians in turmoil, suggesting that they be patient, or change jobs, or buy lottery tickets or stay with abusive husbands. Spirit animals gave Native Americans special insight into hunting or human interactions, or ways to blend into nature.
And me? When I have a complex ethical dilemma, or when I am having trouble prioritizing really important things in my life, I often imagine conversations with my dear, sweet, gentle father, who has been dead over a decade. I present the issues to him, and in my mind, I hear his deep, slow voice, weighing the pros and cons of each set of options. He never "tells" me what to do. In real life, he always lead me to seek my own conclusions. But I imagine his responses, and go through the process of an imaginary conversation with him, and often come up with the answer I was seeking.
The cartoons of my childhood often depicted a devilish creature and an angelic creature, sitting on a character's shoulders and whispering in his ears, offering conflicting advice. Don't know enough about Christianity to say whether this image is based in scriptures, or whether it is a literary creation or just a metaphor for a process of conflict resolution that so many of us can identify with.
You want to play with a tulpa? Ok. I guess. Me? I'll just keep replaying imaginary conversations with my long-dead father in my head. I do not need to create his personality. It is the personality that was responsible for my ethical development, and it sometimes feels like the right place to go when I am in need.
But don't let your tulpas or Jesus or your imaginary friends or some great power from beyond replace your human interactions.