I want to ask about the Hashshaasheen‏ during the Fatimid Era.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

The Hashshaasheen‏ are one of the Ismaa‘eeliyyah sects. All of them are under one banner with the Fatimids. They were in Shaam and Persia. Their beginning was in Egypt by a Persian man called Hasan ibn As-Sabbaah (d. 1124 C.E.). He was called Nizaar. Therefore, they were called the Nizaariyyah (Nizaaris) and they were called the Hashshaasheen‏ because they frequently smoked Hashish. They have the same beliefs of the Ismaa‘eeliyyah such as believing in an infallible Imaam stipulated from the children of Muhammad ibn Ismaa‘eel, the hidden Imaam, raising their Imaams to a degree that is almost equal to Allaah The Almighty, incarnation, the Imaam is the inheritor of all the Prophets and other false beliefs.

They rebelled against the Muslim rulers during their era, and made attempts to assassinate some of them. They had a state called the East Nizaari in Shaam, Persia and the countries of the East. Later, this state was destroyed by the Mongol ruler Hulagu. The last ruler of the Hashshaasheen was Rukn Ad-Deen Khoorshaah (d. 1255 C.E.).

Allaah Knows best.