I’m particularly proud of this website’s Ioun stone guide, a collected list of over 154 different ioun stones from more than 15 different sources. Most are canon D&D sourcebooks, with some from third-party publications. The list has grown by 75% since originally posted, including 43 stones added this month from an AD&D sourcebook and six from a 1991 issue of Dragon magazine.
There’s a surprising amount of background story to the ioun stone. The ioun stone actually predates Dungeons & Dragons, appearing in Jack Vance’s 1973 short story “Morreion”. Vance’s works had a major influence on D&D and the ioun stone made its way into Dungeons & Dragons through The Strategic Review, TSR’s gaming magazine:
"FLASHING SWORDS! #1 (Dell, 1973) contained four excellent swords & sorcery yarns, including "Morreion" by Jack Vance. In this tale there was a magical item of highly unusual value — IOUN stones. Mr. Vance was kind enough to allow us to enlarge somewhat upon his creations and list them as a D&D "Miscellaneous Magic" item."
— The Strategic Review #4, Winter 1975
Dragon Magazine issue #174 (October 1991) describes that according to Vance’s “Morreion”, ioun stones are recovered at great risk from the hearts of obliterated stars.
In that issue’s article, “Bazaar of the Bizarre: Ioun Stones”, Matthew Hargenrader offers a separate origin story for the ioun stones in D&D. Rare ioun stones grow gradually in the Demiplane of Mineral, a place where the Positive Energy Plane meets the Plane of Earth. This plane is hostile to human life and guarded by numerous crystalline creatures, but contains a wealth of gemstones and minerals, including the ioun stones.
TSR’s 1996 book Netheril: Empire of Magic gives an origin story for the ioun stones of the Forgotten Realms setting, where the NPC lich Larloch has a famous preference for the items:
"The Shadow King’s body was in stark contrast to that of Tam. While the Zulkir of Necromancy strove to maintain his human appearance, Larloch was nothing more than a collection of bones partially covered in fine garments. The Netheril lich’s bones were bright white in color, and trails of emerald energy traveled across his form. More than two dozen ioun stones circled his skull, and globes of red light gazed up at Szass Tam as he approached."
— Netheril: Empire of Magic
The book describes the inventor of Ioun Stones, an Netherese arcanist born 4,000 years ago named Congenio Ioun. As this Ioun lived for over 900 years and was an extremely talented spellcaster, it’s not impossible that he ascended to become the deity Ioun of D&D 4th edition.
The earlier Dragon article dislikes the idea that a human wizard might simply have invented the ioun stones, considering it unworthy of the majestic star-cores of Vance’s Dying Earth series:
"This method lacks any spirit of adventure and is very straightforward: It is supposed that ultrapowerful wizards who live on some alternate Prime Material plane simply make these magical gems. The only interesting thing about this origin is that the magical effects created by such wizards are greatly superior to those encountered in a standard AD&D campaign."
—Dragon magazine #174, October 1991, “Bazaar of the Bizarre: Ioun Stones”
I have to admit that I took this approach in Kobold Quarterly #6’s “Rolling Stones”, presenting new 15 new ioun stones as invented by a human inventor named Darven Regance. In deference to Vance’s work and other creation stories I wrote that only these new stones were man-made, and quite likely reverse-engineered from the original stones.
In retrospect, perhaps my character Regance is Congenio Ioun in disguise, or he simply took his “inventions” from the Demiplane of Mineral.