User blog comment:Clovis77th/King Hassan, Horseman of Death?/@comment-29543192-20170116101019/@comment-4802891-20170117070809

Checked. Just as a reminder, the Angel of Death called Azrael indeed isn't Islamic in origins but the nameless executioner of Allah is sometimes refered by the name Azrael or Izra'il by Arabic speakers. It isn't his name, but he is refered as such to make it easier... Just like Hassan is okay with being called something despite not having a name.

About that, I think Hassan i-Sabbah says he has no name because since the time he became the messenger of God, he abandons it and don't need/want to be called by the name again to be recognized. His NP is now what defines him (the sword that cuts head when God says it's time for a head to be chopped off), and in that regard, he is Azrael.

I like your theory. In my opinion, he is the human form of the concept called "Angel of Death" and before him there were no angelic figure mowing down life. Since Heroic Spirits/Counter Guardians can be summoned at any point in time, he might able to appear in the years of old, long before his lifetime.