True Name

A human's True Name is the first name that they recognized applied to them. As a result, it is almost always the name bestowed upon them by their parents.

For mundane humans, a True Name is of little importance. For wizards, it is an important secret to be protected. The invocation of a wizard's True Name can be used to instantly and permanently sever a wizard from their supernatural powers through the Ritual of Naming.

Cultural Significance
Due to the need to keep their True Names hidden, wizards must take up a false name. In ages past, this was an invented name. In modern times, wizards pick a phrase to be used as their name, often specifying which word the name should be shortened to on a familiar basis. For example, Her Merciful Shadow prefers to be addressed as "Shadow" by her friends.

The True Name weakness is the biggest source of distrust between wizards and mundane humans. Wizards, particularly those with a high Power Ranking or equivalent, are nigh invulnerable as long as their True Name is kept hidden. This has led to many ambitious wizards slaughtering their childhood friends and families in order to keep their True Names secret. Alternately, many wizards wait until after their hundredth birthday--when those they knew in childhood have all died--to begin their careers as practicing wizards. This has, in turn, lead to the epidemic of Chronophilia among wizards.

The Circle of Solace uses a specially designed transmutation spell to change a sanctioned wizard's names in the memories of those they knew before sanctioning. However, pundits in the League of Nine allege that many wizards from poor backgrounds have their families unknowingly executed by the Circle, as it is a cleaner solution; while the Circle categorically denies this practice, evidence has been discovered that suggests they did so in the past.

In practice, this leads to wizards being culturally categorized as amoral and ruthless, as only those willing to execute the people closest to them could maintain their powers long enough to become politically relevant.

Phylactery
The Circle of Solace requires a True Name to be provided for each wizard seeking sanction. They use a ritual related to the Ritual of Naming in order to check the accuracy of the provided name. The name, along with a vial of blood, is stored in a Circle tower. These two items are collectively referred to as a "Phylactery," and allow the Circle to find and Name any wizard that is considered a military threat.

Objection to this process was cited as the impetus that led to the creation of the League of Nine. The creation of Phylacteries is illegal under the League constitution.

Here Be Spoilers
Halil makes contradictory claims about the Ritual of Naming. He initially claims that he is safe from being named as "Halil" is a pseudonym, and humans would never be able to recover his True Name. Furthermore, the difference in the shape of the human and Eldest jaw and soft pallet means that no human mouth could speak his name.

He later claims that Eldest are not vulnerable to being Named. Rather, the weakness to the Ritual of Naming was a design flaw specifically inserted into humans as a means of keeping their most powerful individuals from getting out of control. This was an exploit intended to be used by the Eldest, but they went extinct before it became relevant.