From page 66 of Dragon Kings (page 67 of the D&D Classics pdf):
“The inner planes are also connected to the prime material plane via vortices. Commonly known types of vortices are free-standing and temporary. A free-standing vortex to the elemental plane might be in the heart of a volcano, for instance. A temporary vortex is most often a spell such as plane shift. Less commonly known or acknowledged are the living
vortices, creatures of great power, described later.”
… but they are not, in fact, “described later”. They’re talked about at the beginning of the book. But was there supposed to be a monster entry for them in the monster section at the end? Was something cut in editing?
That feels to me like that’s a leftover from changes during development, like they were going to go into more depth, but then things changed as the book progressed and they just never cut or caught that “described later” bit. That happens a lot when doing books - that’s part of what editors are for.
On the other hand, it feels much harder to forget to include a whole section of text or a monster entry, as the writer or someone would have been looking for that missing section to check it over, or it would have had orphaned art, or some other issue to draw attention to its absence…
There is a bit earlier, on page 11 of the book, but as you said nothing else after.
Each had mysteriously become the focus of unlim-
ited elemental magic. Though they couldn’t tap this
power themselves, the sorcerer-kings could impart
that power to their followers, the templars. The end
result was clear, but why this transference of power
became possible remains a mystery, even to the
sorcerer- kings.
In actuality, with the casting of their first meta-
morphosing spells, the sorcerer-kings each attracted
the attention of a very powerful and rare creature
a living vortex. With spidery fingers firmly anchored
in all the elemental planes and the prime material
plane, the living vortex is a continuous conduit of
magical energy. The sorcerer-kings are, until their
deaths, a source of elemental magical power fun-
nelled directly to them by their living vortex, a crea-
ture they don’t even realize exists.
With the passage of centuries, the living vortices
have become extinct. Therefore, no future dragons
will gain the ability to transfer elemental magic to
templars. The original sorcerer-kings will take that
privilege with them to their graves.