They took it from the 1938 book Alamut, which I haven’t read but want to read.

huh, apparently there’s some thought that the author intended to express sympathy for anti-fascist militants. Neat.

For more exciting Ismaili assassin adventures check out ib Munquidh’s Book of Contemplation. He was a Muslim knight (equivalent) during the First Crusade and lived a life. At one point he woke up to his father, uncles, and cousins fighting Ismaili assassins in the halls of his castle. Like the real deal, no cap, not fiction. He wrote the Book of Contemplation as a gift for Salah al-Din. It’s really cool, and offers a completely different view of the relationship between Muslims and Christians during the First Crusade and the period after than the Deus Vult shitheads believe. Plus it’s full of just wild stories - hunting lions, fighting bandits, dealing with day to day life. Cool stuff.