The Old Man of the Mountains
http://www.phinnweb.org/neuro/assassins.html

Hasan began to attract young men from the surrounding countryside, between the ages of twelve and twenty: particularly those whom he marked out as possible material for the production of killers. Every day he held court, a reception at which he spoke of the delights of Paradise... "and at certain times he caused draughts of soporific nature to be administered to ten or a dozen youths, and when half dead with sleep he had them conveyed to the several palaces and apartments of the garden. Upon awakening from this state of lethargy their senses were struck by all the delightful objects, and each perceiving himself surrounded by lovely damsels, singing, playing, and attracting his regards by the most fascinating caresses, serving him also with delicious viands and exquisite wines, until, intoxicated with excess and enjoyment, amidst actual rivers of milk and wine, he believed himself assuredly in Paradise, and felt an unwillingness to relinquish its delights. When four or five days had thus been passed, they were thrown once more into a state of somnolency, and carried out of the garden. Upon being carried to his presence, and questioned by him as to where they had been, their answer was 'in Paradise, through the favour of your highness'; and then, before the whole court who listened to them with eager astonishment and curiosity, they gave a circumstantial account of the scenes to which they had been witnesses. The chief thereupon addressing them said: 'We have the assurance of our Prophet that he who defends his Lord shall inherit Paradise, and if you show yourselves to be devoted to the obedience of my orders, that happy lot awaits you'."

Suicide was at first attempted by some; but the survivors were early told that only death in the obedience of Hasan's orders could give the Key to Paradise. In the eleventh century it was not only credulous Persian peasants who would have believed such things were true. Even among more sophisticated people the reality of the gardens and houris of paradise were completely accepted. True, a good many Sufis preached that the garden was allegorical - but that still left more than a few people who believed that they could trust the evidence of their senses.

The ancient Art of Imposture, by Abdel-Rahman of Damascus, gives away another trick of Hasan's. He had a deep, narrow pit sunk into the floor of his audience-chamber. One of his disciples stood in this, in such a way that his head and neck alone were visible above the floor. Around the neck was placed a circular dish in two pieces which fitted together, with a hole in the middle. This gave the impression that there was a severed head on a metal plate standing on the floor. In order to make the scene more plausible (if that is the word) Hasan had some fresh blood poured around the head, on the plate.

Now certain recruits were brought in. "Tell them," commanded the chief, "what thou hast seen." The disciple then described the delights of Paradise. "You have seen the head of a man who died, whom you all knew. I have reanimated him to speak with his own tongue."

Later, the head was tracherously severed in real earnest, and stuck for some time somewhere that the faithful would see it. The effect of this conjuring trick plus murder increased the enthusiasm for martyrdom to the required degree.