The idea originated from the medieval Teutonic Knights who were a Germanic order similar to the Templars in the holy land but in the Baltic region conquering pagan Slavs. It’s why one of the Nazi symbols is that black cross as this is what the Teutonics wore

Conrad de Monferat was assassinated by THE Assassins during the Crusdaes. In the original Assassins Creed you assassinate his father William de Monferat as a nod to this. If you’re doing a project, I’d recommend reading The Assassins by Bernard Lewis as they did a few throughout the period. Or you could just keep it simple and do Julius Ceasar :)