During the Shockwave, strange marks that became known as "sigils" appeared on the flesh of over one million people worldwide. The sigils appear as rune-like symbols that look to be branded into the skin, and may appear anywhere on a person's body. After the Shockwave, people also began to be born branded with a sigil.

Those who were branded with a sigil during the Shockwave are referred to as the sigil-branded, whereas those born with the marks are known as the sigil-born. There is no difference between being branded with a sigil or being born with one. The term sigil-bearers is the catch-all term for those born or branded with the sigil, although many people prefer to use the term posthuman.

Those branded or born with the sigil find that they can wield otherworldly powers, like the superhumans from comic books and science fiction. It is very rare for one person to be branded with multiple sigils, although someone branded with a sigil may find or learn a variety of ways to use their abilities (such as a sigil-branded individual learning to use their electricity-based powers to manipulate their electromagnetic field and fly).

While most people who bear the sigil find that they have an almost innate sense for and control of their powers, some may find them hard to control during periods of heightened emotional strain. Strength and control of an individual's sigil powers grows with practice and experience, although this may vary among individuals.

A Cipher mage would recognize a sigil as a Cipher mark. Like a Cipher mage's individual Cipher brand, a sigil glows when its power is being used, but usually glows in a colour associated with the power granted, the brightness and intensity varying depending on the strength of the power. Additionally, while a Cipher mage's brand is contained within a simple geometric shape, a sigil is a bare Cipher mark. As the Cipher mages do their best to suppress knowledge of the Cipher, the sigil-bearers are unaware of the true origin of the sigils and their powers, although most assume the sigils are linked to the Shockwave.

During the Shockwave, most people who were branded felt the mark being seared into their skin, although some may have been too distracted by the events of the Shockwave to notice or believed the sensation to be something else.