"genii and fairies, which they believe in as an article of faith, upon the authority of the Koran itself"
Genii or jinn are supernatural creatures in Arab folklore and Islamic teachings, capable of assuming human or animal form and exercising supernatural influence over people. They are understood to occupy a parallel world to humans. Together, jinn, humans and angels make up the three sentient creations of Allah. Jinn are usually invisible to humans, and humans do not appear clearly to them. The Qur'an mentions that jinn are made of smokeless flame or "scorching fire." They may be good, evil, or neutrally benevolent, and have free will. Jinn have the power to travel large distances at extreme speeds and are thought to live in remote areas, mountains, seas, trees, and the air, in their own communities. Like humans, they will be judged on the Day of Judgment and sent to Paradise or Hell.
The Genie as a magical being that grants wishes first appears in the book of the One Thousand and One Nights.