Here, hot off the press, is an NPC from Sisters of the Immaculate Fire for your perusal. I 'blame' Tim Power's excellent novel Declare and its effect on my overly impressionable brain for this. Plus H.P. Lovecraft, although not as much since it's been many a year since I've read any of his work, and all I really remember is the prose style and the fatalism of it all.
Anyway...
Walid al-Ad
The man known to the Red Sisters as Walid al-Ad has many names. He is Walid al-Iram and Walid al-Hatif, Walid ibn-Jinni and Walid bin-Shaitan, Walid the Unspeakable and Walid of the Knife, the Beast of Al-Diwaniyah and the Red Dervish. Whatever he is called, Walid is one of the cruelest and most dangerous men to walk the Earth in these days. He is a twisted prophet of a nameless faith, and a sorcerer and alchemist of frightening skill. It is said that Walid is 105 years old (or, some whisper in the dark before praying that Allah will stop up al-Ad's ears from hearing them speak it, three thousand years old) and that he has outlived many enemies. Today, he is believed to dwell somewhere in the most desolate deserts of Arabia, either west of Ramadi near Baghdad or among the unholy ruins of Iram of the Pillars.
The story of Walid is really a collection of whispered anecdotes and the feverish ramblings of madmen, and little can be said for certain. What is known is that Walid was once an Islamic holy man and a Sufi mystic. But in his travels into the deep desert, he came across the ruins of Iram and was ensnared by the whispers of the ghosts. They gave unto him haqiqa, a vision of the ultimate truth - but not at all the haqiqa accepted by Islamic teaching. Instead, it was a twisted truth passed down from the ages before Mohammed, before Jesus, and before Abraham. Whatever the ghosts of Iram said to Walid, it broke his mind and he emerged from the desert a changed man (his companions, for better or worse, never left the ruins and are believed to have been devoured by the hungry ghosts, or by Walid himself).
Walid drew followers to himself from the wretched and reckless, and his cult soon drew the attention of the Ottoman government. In 1819, Walid was personally denounced as a heretic by the Caliph and Sultan Mahmud II, who attended the bloody execution of Walid's followers over the next three years. Walid has since eluded Turkish soldiers, Arabic tribesmen and the dreaded Hashshashin (an ancient sect of Ismaili holy warriors, generally believed to have been crushed centuries ago but known and feared in the shadows of Arabia today). The Ruwallah Bedouin of northern Arabia say that Walid has begun to gather a new cult from among their people, despite the warnings of their imams and sheikhs, and they say he is planning to awaken something ancient and unholy that sleeps beneath Iram.
Origin: Arabic
Nature: Human
Distinguishing Characteristics: A red scar or birthmark, in the shape of a serpent, upon his forehead. Gaunt, almost skeletal, but with an iron grip.