Ioun stones are specifically derived from the later Dying Earth stories, featuring Rhialto the Marvelous, by Jack Vance. In the first two Rhialto stories, the IOUN Stones are merely powerful items that Rhialto and the other wizards of his time covet. However, the last story, “Morreion,” deals specifically with the source of the IOUN Stones. They are apparently harvested from the interior of a neutron star that has drifted to the very edge of the universe, where a black wall of “NOTHING” disintegrates anything it touches. As the neutron star brushes against NOTHING, its exterior is cut away, revealing the IOUN-Stone-laden interior, which can be harvested.

This is also covered in this RPG Stack Exchange question. However, the specific reference to The Strategic Review #1 appears to be erroneous; while that issue contains the first description of the mind flayer, I do not see any mention of ioun stones in that issue.

 (Moreover, the first book in the second cycle of Amber novels was not published until 1985, while the Dungeons & Dragons ioun stones are about a decade older.)

Ioun stones are specifically derived from the later Dying Earth stories, featuring Rhialto the Marvelous, by Jack Vance. In the first two Rhialto stories, the IOUN Stones are merely powerful items that Rhialto and the other wizards of his time covet. However, the last story, “Morreion,” deals specifically with the source of the IOUN Stones. They are apparently harvested from the interior of a neutron star that has drifted to the very edge of the universe, where a black wall of “NOTHING” disintegrates anything it touches. As the neutron star brushes against NOTHING, its exterior is cut away, revealing the IOUN-Stone-laden interior, which can be harvested.

This is also covered in this RPG Stack Exchange question. The stones first appeared in The Strategic Review, vol.1, no. 4, published in 1975.  (Thanks to Daniel R. Collins for tracking down the correct reference and editing that answer to reflect it.) Note that the first book in the second cycle of Amber novels was not published until 1985, while the Dungeons & Dragons ioun stones are about a decade older.

Ioun stones are specifically derived from the later Dying Earth stories, featuring Rhialto the Marvelous, by Jack Vance. In the first two Rhialto stories, the IOUN Stones are merely powerful items that Rhialto and the other wizards of his time covet. However, the last story, “Morreion,” deals specifically with the source of the IOUN Stones. They are apparently harvested from the interior of a neutron star that has drifted to the very edge of the universe, where a black wall of “NOTHING” disintegrates anything it touches. As the neutron star brushes against NOTHING, its exterior is cut away, revealing the IOUN-Stone-laden interior, which can be harvested.

This is also covered in this RPG Stack Exchange question.

(Moreover, the first book in the second cycle of Amber novels was not published until 1985, while the Dungeons & Dragons ioun stones are a decade older.)

Ioun stones are specifically derived from the later Dying Earth stories, featuring Rhialto the Marvelous, by Jack Vance. In the first two Rhialto stories, the IOUN Stones are merely powerful items that Rhialto and the other wizards of his time covet. However, the last story, “Morreion,” deals specifically with the source of the IOUN Stones. They are apparently harvested from the interior of a neutron star that has drifted to the very edge of the universe, where a black wall of “NOTHING” disintegrates anything it touches. As the neutron star brushes against NOTHING, its exterior is cut away, revealing the IOUN-Stone-laden interior, which can be harvested.

This is also covered in this RPG Stack Exchange question. However, the specific reference to The Strategic Review #1 appears to be erroneous; while that issue contains the first description of the mind flayer, I do not see any mention of ioun stones in that issue.

(Moreover, the first book in the second cycle of Amber novels was not published until 1985, while the Dungeons & Dragons ioun stones are about a decade older.)