I've never seen a thread 'bout them, so why not make one?
Tulpas are basically self-induced hallucinations, something like an imaginary friend, although it is more self-aware and if you create it right it will appear independently of your will. I have started the process of creating mine, it (an ammount that varies, depends on your personality and will) should take about 50 hours of meditation. You can create one in two ways, first the personality and voice (when you create one you will have to discuss their appearance with them) or the appearance first (the way I've gone with, it's a voiceless being, in my case a wild west cowboy, decided to go with that). The word and belief of the fact Tulpas exist originates from Tibet, you can read some of Alexandra David-Neel's works, she was an orientalist back in the 1800s. Her Tulpa actually became sentient and started working against her, so she had to absorb it back into her mind, which was harder than creating it. What's the point of creating one? Well, if you manage to create an useful one, you can use it to extract knowledge from your sub-conciousness (f.e. someone from your family put something in some place, your conciousness doesn't remember where, but you have definitely seen it. You can then ask your Tulpa where it is and in that case it will tell you the truth. You can't however use it to get the information about some place you haven't been to, because if you ask your Tulpa to do the above for you, it will definitely lie). The most important thing in creating that being is believing it can be created. It's a hallucination, therefore you have to pretty much hypnotize yourself. Well, take your time and good luck.