There is an old article in issue #12 of The Dragon that is of interest to our discussion on sword & sanity gaming. The article was written by Rob Kuntz, and titled “The Lovecraftian Mythos In Dungeons & Dragons.” The introduction explains that the intention of the article is to present the Great Old Ones, as well as various other entities found in the Cthulhu Mythos, in D&D terms, and is laid out in a way to be compatible with Dungeons & Dragons supplement IV “Gods, Demi-Gods & Heroes.”
What follows is a series of entries for the Great Old Ones: Azathoth (Creator of the Universe), Cthulhu, Hastur the Unspeakable (Him Who Is Not To Be Names), Nyarlathotep (the Crawling Chaos, the Messenger of the Gods), Shub-Niggurath (Black Goat of the Woods with a Thousand Young), Cthuga (Lord of Fire), Ithaqua (Lord of the Air, Windwalker), Yig (Supreme God of Serpents) and Yog Sothoth (the Key and Guardian of the Gate). There is a writeup for the Necronomicon by Abdul Alhazred, as well as the Elder Sign. The article ends with a quick selection of “Inhuman and Partly Human Races of the Cthulhu Mythos.” These include: Byakhee, the Deep Ones, the Great Race, the Old Ones, the Mi-Go (the Fungi from Yuggoth, the Abominable Snow Men) and finally the Shaggoths (sic, Shoggoths).
My first introduction to the Mythos in a gaming context was through the AD&D (Special Reference Work) Deities & Demigods Cyclopedia, which was published in 1980. This edition included a whole chapter on the Cthulhu Mythos, richly illustrated by Erol Otus. Later editions of this work would not include this section of the book due to copyright infringement. What is interesting is that the Dragon article detailed above outdates Deities by at least a couple of years.
Obviously, the Great Old Ones are not meant to ever be challenged in combat, so why was it necessary to document these entities in D&D terms? This is a question that has no logical answer, but it is still interesting to see the write-ups, and how they are interpreted in game terms.