The Assassins did anything without question that the Imam asked.  Because of their devotion, the Assassins were able to disrupt the Mongol army on its invasion of the west.  The Mongol invasion of the West was stymied by the Nizari Ismailis until the Mongols were able force the surrender of the Alamut Castle located here and the capturing of the Imam.

The term assassin comes from this Muslim sect - a mispronunciation of the term hashishiyya.

Assassins

Assassins (Persian: حشاشين Ḥashshāshīn or باطنیان Bāteniān) is a misnomer for the Nizari Ismailis applied abusively to them by the Mustali Ismailis during the fall of the decaying Ismaili Fatimid Empire when the two streams separated from each other. In 1122 the Mustalian dynasty Fatimid caliph al-Amir referred to the Nizaris separated from them and "now firmly established in Persia and Syria", abusively as the hashishiyya "without any explanation" and "without actually accusing them of using hashish, a product of hemp".

• http://en.wikipedia.org/wiki/Assassins
• Pages 178-180 - Weatherford, J., 2004, Genghis Khan and the Making of the Modern World: Three Rivers Press, New York, 312p.