The Order of Assassins or simply the Assassins were a Nizari Isma'ili order that existed between 1090 and 1275 AD, founded by Hasan-i Sabbah.
Masyaf Castle in Hama. It was the headquarters of the Assassins in the Levant. Picture taken in 2017
Edward I, King of England thwarts an attempt at his life by an Assassin and kills the attacker. The assassin likely was sent by the Mamluk Sultan Baibars, in order to remove his opposition to a 10-year truce with the Christian states at Jerusalem. 19th-century depiction by Gustave Doré
View of the city of Alamut being besieged. 1438 depiction by the Tarikh-i Jahangushay
Remains of the Alamut Castle in Qazvin, Iran
Hasan-i Sabbah, also known as Hasan I of Alamut, was a religious and military leader, founder of the Nizari Ismai'li sect widely known as the Hashshashin or the Order of Assassins, as well as the Nizari Ismaili state, ruling from 1090 to 1124 AD.
Engraving of Hasan-i Sabbah riding a horse
The Hashshashin's fortress of Alamut Castle
Hasan-i Sabbah as depicted in Livre des merveilles