Thought-forms are energetic beings created for the purpose of performing a task. Some practitioners of the Craft, including myself, use Thought-forms for a variety of intents and purposes.
They have been called by various name throughout history. The Tulpa, a type of Thought-form, dates back to ancient Tibetan Buddhism. There are also certain instances where the term “Fetch” is used as a name for them. I tend to avoid using the word Fetch because, in Irish folklore, the appearance of a Fetch–or double of a person–has ominous tones and generally portends the death of the person it’s mimicking. I use the word “Seeker” for Thought-forms, as this was the term used in one of the magical traditions I studied.
Thought-forms are created by the practitioner energetically by raising and concentrating energy. The exact purpose or intent of it is up to the practitioner and their own Craft practices and guidelines. Once created, Thought-forms can work independently from their creator. A common practice is the use of them for assistance on the Astral Plane or protection.
The creation of Thought-forms is not to be taken lightly. If left with no task to perform, it can wander off and cause mischief, or worse. In most cases a practitioner will create a Thought-form for a specific task to be completed within a specific period of time. Once the task is completed the practitioner energetically disperses the Thought-form. This eliminates the chance of the Thought-form acting and its own and doing something the practitioner did not intend for it to do.
I find the use of Thought-forms to be an essential part of my Craft. Learning to create and work with Thought-forms does require time and effort, however. I would suggest finding a qualified teacher who is experienced in energy work and Thought-forms if you are interested in learning about them.