Okina Yama, also known as King Hassan, is a pivotal character in the Fate/Grand Order series. He is the first Hassan-i-Sabbah, also referred to as the 'Old Man of the Mountain.' As a Servant, he is summoned under the Assassin class. His role is significant as he embodies the concept of death itself, wielding the authority to sever life with his sword. His stoic demeanor and unwavering dedication to his duty create a formidable presence, making him both a feared and respected figure within the narrative.