The Jinn were part of pre-Islamic Arabia's mythology which were later incorporated into Islamic theology. In 2009 they were first used as a fictional race by Chaosium for the Call of Cthulhu RPG.
The Jinn are a race of beings from another dimension who were brought to Earth by Taranushi an Outer God. For a while they treated Earth as a playground, tormenting humans. Upon the death of the sorcerer who summoned Taranushi, they found themselves trapped on Earth, unable to return back home. Enraged they rebelled against Taranushi, and though their attacks were repelled, he was unable to reestablish his control over them.
Like Taranushi the Jinn likewise appear as insubstantial beings, as if made of smoke. No two jinn are alike and the race consists of several sub-species which are the Marid, the Ifrit, the Dalham, the So'la, the Hofafa, and the Ghul. Like their former master, they too sometimes take human forms. The various jinn factions claimed territory on Earth, establishing themselves in the ancient Middle East.
During the time of the Romans, the Marid who were the most powerful of the jinns, claimed the oases, mountains, and seas of Arabia Magna (the Arabian Peninsula) and Cyrenaica (eastern Libya). Huge greyish creatures of great strength and short tempers, that are susceptible to flattery and therefore can be persuaded to show mercy if praised enough.
The Ifrit are the 2nd most powerful type of jinn. Incredibly cunning beings who claimed the underground caverns, where they established a great kingdom. Only going to the surface to capture human slaves whom are lured to ruins. The Dalham appear as handsome camel riding middle-aged men, who prowl the desrt islands. With their powers they sink ships, devouring the drowned sailors and sometimes even those who manage to make it to shore.
The So'la are the most vindictive of all the jinn. Seeing humans as cattle to be hunted and devoured. When they attack humans, no one survives. The only witnesses have been those whom were well hidden or saw the assault from a distance. The winged Hofafa rule the skies over Cyrenaica and Arabia Magna. Though not as vindictive as the So'la, they ravage the people and land, making them pay for the jinn being trapped on Earth. The Ghul are malicious jinn who claimed the night. Though less powerful than either the Marid or Ifrit, the shape-shifters are considered by many to be more dangerous.