From Akashic Records
A Sigil is a symbol that produces a magical effect. Sigils have seen prominent use both historically and in modern times.
Historically what denoted a sigil was extremely varied. The only true criteria was that it be an image and have magical properties.
Modern sigils have their root in the work of Austin Osman Spare. Spare was an artists from the first half of the 20th century who combined his artistic inclination with his belief in magic. Spare began the practice of forming words and letters into magical glyphs of desire. These glyphs would then go about affecting the creator's reality so as to produce the desired effect.
Spare's new form of sigil would go on to be a major influence in the creation of chaos magic. Spare's form of sigilization allowed anyone to turn their desires into a sigil, and do it in whatever way they saw fit. The independent nature of the new sigil helped to promote the individualist and creative ideals that came to be embodied in chaos magic.
Although many methods of modern sigil making are heavily based off Spare's practice of turning words into glyphs, some magicians are very abstract about the form their sigils take. They have been known to sigilize their desires as art, poetry, prose and even as mantras or songs.
Other Types of Sigil
A particular subset of sigils are those that serve as the name of a particularly entity. In antiquity, these entities were usually either angels or demons. In modern times a sigil could be the true name of almost any entity a magician might encounter.
In particular, many chaos magicians are in the habit of creating Servitors. Many use sigils to create these magical servants. With Servitors the sigil functions not only as its true name, but as the root of its entire existence.
A hypersigil is an extended work of art that the creator has made to function as a sigil. Grant Morrison's comic The Invisibles is claimed to be a hypersigil.
Linking sigils are those that are designed to connect with one another. The uses of a linking sigil are as varied as those who make them, but a very common usage is to gather magical energy from many separate places into a single point. Conversely, many linking sigils are also used to share a single store of magical power between multiple magicians, items, or locations.
Arguably the most notorious and powerful linking sigil is Ellis.
The Steps to Make a Sigil
Statement of Intent
Vital to the creation of a sigil is the Statement of Intent. The SOI is basically the desire that the magician is creating the sigil to fulfill. For example, if a magician were to need a new car, his SOI would be, "I wish to find a new car at a great price." Details could be added to the SOI as the magician saw fit.
After the SOI has been established it must be sigilized.
The most popular method is to reduce the SOI to its basic form. In other words, "I wish to find a new car at a great price," would become, "iwshtofndaecrgp.'
The above method of reduction was to simply remove all repeated letters. Some other methods also remove all vowels from the SOI.
After the reduction, the remaining letters should be reconstructed in a way that the creator feels is most 'magical.'
Fire and Forget
After the sigil is created, a magician needs to 'fire' it. There are many methods by which to 'fire' the sigil, but nearly all methods incorporate some form of Gnosis.
After the sigil is fired, it is important that magician forget the original SOI.
Many often point out that this seems to be a fault, because if forgotten there would be no way to tell if the sigil had worked. This can be explained by the fact that the magician isn't supposed to forget the SOI completely, but to merely avoid thinking about it consciously.
The reason it is necessary to forget is because additional desires and want of result, even after firing, can interfere with the original SOI, delaying or even bastardizing the final result.