Truenames

Purportedly first discovered by the Magisters of the Green College in the 8th Century CE, every person, object, and even concept has a unique 'signature', known as a Truename. Truenames are not magical in the classic sense, but are a kind of inherent property of reality, an entity's 'shadow' on the metaverse. Truenames are not given, are generally not known by those they identify, and are not in common use. Indeed, 'Name' is something of a misnomer, a Truename is not anything that can be *pronounced*, or neatly categorized in any real way - it's more of an abstraction that happens to be unique, and therefore useful. Truenames are difficult to measure, with commonplace techniques measuring the subject's reaction to various stimuli - usually, this mean extensive magical scanning, discerning truenames using mundane technology alone is virtually impossible. By cross-referencing numerous such data sources, a Truename can be discerned. While a Truename is abstract, they can be measured and represented in numerous different ways, from song-like flux sequences to high dimensional matrices to arcane patterns burnt into crystal. These representations make meaningful use possible, alongside 'dictionaries' cross-referencing Truenames to what they represent.
The primary usage of Truenames is in identification - Spells can be programmed to react to a particular Truename, working as both a more reliable form of targeting (eliminating chance of failure due to ambiguity), and a form of authentication (so that something can only be used/accessed by authorized persons). Alternative uses are largely speculative. Whether Truenames are essentially random or hold some yet undeciphered meaning is hotly contested, but similar entity do seem to have similar Truenames. Reversing this to predict the nature of an entity from its Truename (or accurately predicting Truenames from an entity's nature) is a covet goal, but has not been demonstrably achieved.
Even more speculatively, some believe that Truenames are part of the way the multiverse discerns a creature's origin, thus it is intimately linked with planar boundaries - the plane detects a 'wrong' Truename and rejects it. This would enable both improving and evading banishment magic, and, theoretically, with enough power, it may even be possible to effectively 'erase' a target's Truename, effectively banishing them from the multiverse. How this could be done, let alone the consequences, are a matter of speculation.
Truenames are not truly unchanging, but under normal circustances, change so slowly that it suffices for most practical purposes. While long term studies have not been satisfactorily conducted (by mortals, anyways), it is suggested that for typical persons, deviation sufficient to induce ambiguity (for flex-factor authentication methods) will occur after approximately 800 years, up to five times that for Transcendent. However, significant alteration of an entity's nature can alter their Truename - most significantly, the dead (neither soul nor body) cannot be identified by Truename¹ - they are essentially given an entirely new name. Persons are fairly resilient against this kind of deviation, while non-living entities are more plastic. It is possible, though extremely difficult, to deliberately induce a significant alteration in Truename, typically to escape a trace. This is essentially done through targeted deep reconstruction with an emphasis on 'minimal' alteration... but it's still deep reconstruction.

1: Which means the disappearance of person's Truename can be used as proof-of-death.

Type

Metaphysical, Astral