Not much is known about the hashashin. But the training was brutal. They were mentally and physically pushed to do horrible things. Not many survived the training.
All warriors followed the Turasiyga or Islamic warrior code, where they are trained in combat, disguises and equestrianism. Codes of conduct were followed as well, being taught in the arts of war, protection and secrecy.
Due to being dramatically outnumbered in enemy territory, the Hashashin tended to specialise in covert operations. They would often assimilate themselves in towns and regions of their targets and over time, stealthy insert themselves in to strategic positions.
The history of these people is very vague, But they were feared very much by there enemies. I think that these people will be remembered for a very long time.