First, please use proper terminology.
Tulpa is a Tibetan word, and refers to actual, physical beings created by thought. They are NOT servitors or thoughtforms. They are as flesh and blood as any human.
The book that brought the word into the lexicon of the New Age was “Magic and Mystery In Tibet,” by Alexandra David-Neel. If you actually read that book, you will see that a tulpa is NOT synonymous with the Western concept of a “servitor.”
Two, I completely disagree with this.
Sorry to burst your bubble, but if you don’t believe servitors are real, then Yog-Sothoth cannot be real either, because HE WAS MADE UP BY THE AUTHOR HP LOVECRAFT AND DID NOT ACTUALLY EXIST UNTIL HE WAS PUT ON THE PAGE.
You can easily make the argument that Yog-Sothoth is a thoughtform created by Lovecraft, and given greater “life” by his writing circle, who took the idea and ran with it, and by the fans who read the fiction over the last 100 years.
The word “Necronomicon” didn’t exist until Lovecraft created it, and now it is synonymous with books of “evil” black magick and there have been half a dozen books with that name released into the collective consciousness.
You can’t trot out the creations of Lovecraft to prove servitors aren’t “real,” because the Cthulhu Myhos isn’t real either.
Other fiction people have successfully used magically include Atlantis, the Akashic Records, Harry Potter, The Chronicles of Narnia, DC and Marvel comics, and the works of Stephen King.