by Will Durant, page 309 - 310, THE AGE OF FAITH  (CHAP. XIV)

The assassin was a member of the strangest sect in history. About 1090 an Ismaili leader - the same Hasan ibn al-Sabbah whom legend allied with Omar and Nizam - seized the mountain fortress of Alamut ("Eagle's Nest") in northern Persia, and from that stronghold, 10,000 feet above the sea, waged a campaign of terror and murder against the opponents and persecutors of the Ismaili faith.

It was a secret fraternity, with diverse grades of initiation, and a Grand Master whom the Crusaders called the "Old Man of the Mountain." The lowest degree of the order included the fidais, who were required to obey, without hesitation or scruple, any of their leader's commands. According to Marco Polo, who passed by Alamut in 1271, the Master had arranged behind the fortress a garden peopled like the Mohammedan paradise with "ladies and damsels who dallied with the men to their hearts' content." The candidates for admission to the order were given hashish to drink; when stupefied by it, they were brought into the garden; and on recovering their senses they were told that they were in paradise. After four or five days of wine, women, and good food, they were again drugged with hashish, and were carried from the garden. Waking, they asked for the lost paradise, and were told that they would be readmitted to it, and forever, if they should obey the Master faithfully, or be slain in his service .

The youths who complied were called hashshasheen, drinkers of hashish - whence the word assassin. Hasan ruled Alamut for thirty-five years, and made it a center of assassination, education, and art. The organization long survived him; it seized other strongholds, fought the Crusaders, and (it is alleged) killed Conrad of Montferrat at the behest of Richard Coeur de Lion.