The Ahl al-Jabal are a hunter compact featured not in any Hunter book, but instead in the Vampire: The Requiem book Ancient Bloodlines.
Created during the initial Medieval Crusades, the group splintered from the ancient order of Hashshashin, known more commonly as assassins. Rising from the many splinters in Islam's history, the group was formed when a Hashshashin leader Sinan, and the Sultan Saladin came to realize that monsters who sucked the blood of the living were infiltrating their armies and strongholds. Nearly destroying each other, the two moved on from each other, vowing to create a group of dedicated hunters against the monsters.
Since then, the compact has used it's position in Islamic countries to create a close knit, highly effective group of vampire hunters, as well as using prison populations in the U.S. to bolster their numbers internationally. The group is not fanatical, however, and prefer to use the least destructive means to destroy the monsters. To the Martyrs, collateral damage is just as disgusting as the monsters themselves.