Chaos magic is the youngest current in this field, worked out in England in the late 1970s principally by Peter J. Carroll and Ray Sherwin, who founded the Illuminates of Thanateros around 1978. What it discarded was the inherited metaphysics, the fixed Tree, the tables of correspondence, the insistence that one system was true. What it kept was technique, above all the sigil.
Its signature idea is paradigm shifting: that a belief is not something one holds because it is true but something one adopts because it is useful, to be put on for a working and taken off afterwards. A practitioner might run one operation inside a Norse frame and the next inside a quantum-physics metaphor, treating each as a set of controls rather than a creed. The slogan borrowed for this, by way of William Burroughs, is "nothing is true, everything is permitted." The result is deliberately results-oriented and close to psychological experiment, which is both its appeal and the basis of the common criticism that it collapses into a theatre of self-suggestion.
The current is also where the vocabulary of made entities is most developed, and these terms are worth distinguishing because they are constantly confused.
A thoughtform is the general and oldest of them, a term the Theosophists Annie Besant and C. W. Leadbeater put into circulation in 1901 for a mental image held to take on a subtle-matter existence of its own.
A servitor is a thoughtform built on purpose and given a task, a small, deliberately constructed psychological or magical agent, created, named, charged, set to work and, in careful practice, dissolved when its job is done.
An egregore is the collective version: the shared thoughtform of a group, an order or a movement, held to take on a momentum the individual members no longer control. The word is older than chaos magic, reaching back through nineteenth-century French occultism to a Greek term for a 'watcher'.
A tulpa is the odd one out, and the term most often misused. It entered English through Alexandra David-Neel's 1929 travel memoir as her rendering of Tibetan sprul-pa, for a being she said an adept could project into apparent independent existence; she reported creating one and then struggling to be rid of it. The Tibetan source concept is more technical and less lurid than her account, and the word has since been taken up again by an online 'tulpamancy' community for a self-created imagined companion, a use with no connection to either the Tibetan doctrine or the magical one beyond the borrowed name.
In every case the honest description is the one practitioners themselves often give: these are techniques for externalising and working with parts of one's own mind. Whether anything is created that outlasts the belief in it is exactly the point on which the tradition does not agree with itself.