Tulpa: Tibetan Spirit Sigil

A Tulpa is a "physical materialization of a thought, resulting in the creation of a being or object." (Pad of Definitions, Official Website)

Creation
A Tulpa can be created by many people concentrating on a one thing while looking at a Tibetan Spirit Sigil. Once created a Tulpa takes on a life of its own and no longer needs people to believe in it.

John Winchester's Journal
There are a few notes about the Tulpas creation and meaning:

May 15
Tulpa created through intense ritual visualizations known as dubthab. Variation known as dragpoi dubthab is specifi cally aimed at creating a thoughtform with the idea of harming another person. Physical form of tulpa becomes apparent to the senses after the mind can begin to sense its spirit presence.

Tulpa thus created, no matter the creator’s intent, will gradually turn on the creator. Evans-Wentz wrote that enlightened magicians can destroy tulpa as easily as create them—also that those masters can incorporate their spiritual being into the body of another person. It’s about the willpower.

Appearances

 * Season 1
 * Hell House
 * Season 8
 * Hunteri Heroici (mentioned)