The Assassin's Guild -- HASHSHASHIN
In 1094 the religious control of Egypt was thrown into civil war as two sons fought over the succession from their dead father. The Hashshashin (assassins) were partisan supporters of the eldest son, Nizar, who seized and fortified a string of mountain strongholds in northern Persia These included Alamut in the Elburz Mountains, and Syria. From these fortresses they waged a campaign of terror against both orthodox Muslims and the Christian Crusaders. They often murdered prominent individuals - resulting in the word "assassin" coming to mean a politically motivated murderer in the English language.
Some of the Templars and Hospitallers most formidable castles were built near the Hashshashin's Syrian domain, including Krak des Chevaliers and Saone - arguably the most defensible castles in the world. The presence of such a sizeable and elite military force compelled the Assassins to pay a tribute of gold - a tribute that allowed them to keep their mountaintop realm independent of Christian control for almost a century. Among the Hashshashin was a vampire bloodline - the Assamites. After initially fearing the appearance of God's warriors, an Assamite elder sought to turn their presence to advantage.
Tentative negotiations took place for several years, eventually convincing the knights that the Assamites would be useful in their crusade against the blood of Cain. The Assamites, for their own reasons, also sought the death and destruction of kindred - thus a tenuous treaty was formed. If the Assamites assisted the knights, their realm would be inviolate - never to be attacked by the Church.
While cooperation was limited, both sides benefited from information supplied by the other.
A powerful vampire masquerading as the Patriarch of Jerusalem was, in 1214, killed by the Hashshashin Assamites - hired by the Hospitallers to make it look like a Muslim action.
The Hashshashin made a critical mistake in the murder of Genghis Khan's son, Jagati, who ruled part of Persia. Jagati had offended the Ismali's and Hashshashin by forbidding certain rituals involved in prayer and slaughter of food animals.
In 1256, the Mongols took their revenge. Most of the Hashshashin were killed and their mountaintop fortresses destroyed. The Church Knights, already weakened by Mongol incursions and civil war, did not send assistance.
The Hashshashin leader, Rukn ad-Din Khurshah, sought to negotiate with Mongu Khan. He failed to obtain an audience, and he and his party were murdered while returning home. Later, his family was captured and subject to long and tortured deaths.
The relationship between the Militant Orders and the Hashshashin was always a shaky one. By the fall of the Holy Land in the late 13th century, the alliance had been forgotten. The Hashshashin and Assamites - though greatly reduced by the Mongol Horde - were subjugated by the Mamelukes in 1273 and fought by their side as the Christians were gradually repulsed from the Holy Land.