True Names

The magic of true names is believed to pre-date The Before Times and has ties directly to the powers of the gods themselves. There have been ancient texts recovered throughout history that mention this archaic and dangerous power, but only in broken context. Those that seek this knowledge have been unsuccessful, and it is believed a fool's errand by many arcane practitioners.
It is said that a true name is a creature's hidden name that, rather than just acting as a label, metaphysically truly belonged to that creature. All beings have true names, though most of these are unknown, especially to mere mortals. Knowing a creature's true name could grant power over it.
According to these legends, True names are given to all creatures through an agreement between the gods in an effort to control them. They were supposed to be kept secret, but some were allegedly leaked out by one or more powers. It is rumored that a true name could be learned from a being known as the Knower of Names, believed to have resided in the layer Cania in the Nine Hells. This entity supposedly knew all true names but was limited in telling them by the gods' demanding a sizable monetary sacrifice from the asker for each name. Whether or not this entity truly existed remains a mystery; aside from a this little information, nothing has been uncovered about this Knower of Names.
If a creature's true name was known, a caster could use it to cast powerful spells to harm, bind, or control the creature. It could also be used to bind a summoned fiend to make a pact it would be compelled to keep.   Each creature had a unique true name among the Words of Creation, a language so primal even speaking a word of it had a powerful effect. An individual who could obtain knowledge of this language could learn a creature's true name and use it to weaken it and bend it to their will.
Additionally, it was thought to be possible that, when an individual's true name was spoken, they fell under the complete control of the speaker, directly compelled to do anything they ordered.