History of Islam Vol 3 of 3 by Akbar Shah Najeebabadi

Kingdom Of The Qaramatians Batinians Of Pers ia 283
founder of a new faith and sect. He came to be addressed as "Sayedna"
by his followers. He passed thirty-five years of his life in the Alamut
Fort and he did not come out of the Fort for a single day.
Death Of Hasan Bin Sabbah
He died on Rabia al-Akhir 28, 518 A.H. at the ripe old age of 90. He
collected human material from wild and savage men of hilly areas and
turned them into such a fortified band and they would do anything at
the command of their leader. They were known as the party of
"Fidais" (pledged devotees). Aided and abetted by these "Fidais" it
became easy for him to get powerful kings, commanders and
antagonists assassinated in their own houses and, in this way, he had
became a terror to everyone.
Kiya Buzurg Ummid
After the demise of Hasan bin Sabbah, one of his disciples named Kiya
Buzurg Ummid, succeeded him and occupied Alamut Fort. His
dynasty reigned up to 655 A.H. Kiya Buzurg Ummid was succeeded
by his son Hasan bin Muhammad who was succeeded by his son
Muhammad, the second bin Hasan who was succeeded by Alauddin
Muhammad bin Jalaluddin Muhammad who was finally succeeded
by Khurshah bin Alauddin.
Ruknuddin Khurshah
He was the last king of the "Fidais" who was arrested by Hulagu
Khan the grandson of Genghis Khan and part of the Khan dynasty
and his country and empire were destroyed with the destruction of
Baghdad.
Although the Fidais ruled over Alamut Fort and its suburbs
for about one hundred years, during this long period the entire
territory witnessed no sign of progress or development. When
Genghis Khan began to ravage Muslim countries, the Fidais also
sprang into action with their expansionist designs. They were still
fulfilling their plans when they were invaded by Alauddin Khwarizm
Shah who struck a deadly blow to their power. He wrested from them
all the forts and razed them to the ground allowing them all to take
refuge in Alamut Fort. At last, Hulagu Khan put them all to death.