The Aklo language is a fictional language system which appeared in Arthur Machen's short story The White People. H.P. Lovecraft used the Aklo in a number of his stories, most notably The Dunwich Horror and The Diary of Alonzo Typer. It appears as a key element of Alan Moore's Cthulhu Mythos work The Courtyard.
The Aklo language and script was first used by the Serpent Men some 1.5 million years ago, during the Pleistocene epoch. It is unlikely that this language was in every day use. It may be that Aklo was a ritual language only used by the priestly castes in ceremonies. There is a possibility that the Serpent Men learned Aklo from the Old Ones (the lesser children of Yog-Sothoth) since those beings are known to respond to summons spoken in Aklo. To this day the Aklo language is still employed in certain spells and rituals.
Although Aklo can be used for communication, its primary usage is in incantations and prayers. Below is a list of some of the magical rites that Aklo is employed in.
- The Aklo Unveilings are a collection of 48 revelations recorded by the Aklo. There is said to be a 49th Unveiling, which mankind will only learn when Glaaki calls humanity to him.
- The Aklo Formulae are a collection of incantations connected with the summoning, banishing and controlling of certain extradimensional beings. The Third Aklo Formula can be used to make invisible and immaterial entities reveal their physical form.
Since the Aklo language is still in use today, certain cultists and sorcerers may have records and codices in this language. One of the best known public records of the Aklo language is the Unaussprechlichen Kulten which contains a key to deciphering the Aklo lettering system and a rudimentary dictionary. The Aklo Tablets (also known as Aklo Writings or the Aklo Book) appear reproduced in the book Remnants of Lost Empires.