True Word
It is said that the Dreamer spoke, sang, and danced the world into existence. The words it spoke were not those of a mortal language--they outright embodied truths about the nascent reality and gathered the mists of the Dark Beyond around themselves, taking solid form as the 8+1 Primordials. In essence, those entities were living clusters of Words, instantiations of complex concepts given life by the Dreamer's power and the reactive nature of the Dark. The lesser concepts and progenitor races were formed as those Primordials fractured sub-concepts and gave them independent life to handle more things at once.
Being made of Words in their full form, the primary power of the Primordials was over those Words and anything composed of them--rewriting, adding, and subtracting at will. But only the Dreamer itself could speak totally new Words, bringing new concepts into existence ex nihilo. None of his creations had the innate control over the substance of the Dark, being but subordinate dreams. They owed their very existence to It, drawing sustenance from its eternal flame.
After the Dawn War
In the aftermath of the Dawn War, the Primordials were no more--their Words were used to anchor the new-born planes (other than the Nameless, who was confined in the Abyss). Some of the lesser concepts still existed in their fallen, Broken Concept form, but were also exiled from reality. The Dreamer, too, was no more a physical entity, its self having gone into the Great Mechanism. The multitudes of mortals had been created, with their temporary natures and supernal ability to create, as if they themselves could Dream.
But the True Words continued, if only in fragments. All of the immortals (including lucians and denizens of the elemental planes) are, at their core, True Words of varying complexity. Usually just a fragment of words and "letters"--the dot of an i, the tail of a script a, etc. This is both a strength and a weakness--as long as the Words are not absorbed into another Word, the immortal will reform even if its body (which is aether bound and condensed around that central truth) is destroyed. In essence, only another immortal or a jotnar can completely destroy an immortal. On the other side of the coin, the fixed nature of the Words and the lack of anyone who can truly speak these words means that immortals can only change in limited ways unless they absorb another immortal's Words. They are bound to the fragments of meaning that their Word embodies. This includes those mortals who gave up their Sparks in exchange for Words during their ascension, securing immortality at the price of growth. Immortals also depend on external energy for their existence, not being able to create their own. And those that depend on worship become what is worshipped, to a greater or lesser degree.
Magic And True Words
Magic, as it is seen among mortals, involves manipulating true words. "Arcane writings" are fragments of written representations of True Words; verbal components are tiny fragments of True Words, and material and somatic components are the physical and rhythmic echoes of the Dreamer's dance and song in the beginning. It is said that the runic powers of the Titans and the spoken sorceries of the Wyrm, along with the All-song of Leviathan, were truer, purer renditions of those primal Words.
