Assassin (Fate/Grand Order - King Hassan)

Assassin (アサシン) is an Assassin-class Servant able to be summoned by the Protagonist in the Grand Orders of Fate/Grand Order. He is a Grand Assassin (グランドアサシン). He removed himself of his rank of "Grand" during the battle with Tiamat.

Identity
Assassin's True Name is Hassan-i-Sabbah, the founder of the Hashashin; the first to take upon himself the title of "the Old Man of the Mountain" (山の翁) and the name of Hassan-i-Sabbah. Even so, his actual identity was unknown even to the eighteen individuals who came to inherit his titles. Proof that he in fact existed is nowhere to be found -- except in the certainty that if ever he who takes the seat of Hassan-i-Sabbah strays from his path, there shall come an executioner to part him from his head.

There was within the sect of the Hashashin not a single witness who could attest to the existence of the original Hassan; all of those who encountered him met their end. He who forged the name of "the Old Man of the Mountain" elected to live as an observer who would enact judgment upon the rot and the deviations of the sect. Even though the sect persisted in righteous accordance to the doctrine of Allah, it was inevitable that those avowed to carry it forth would come to sin in the eyes of Man. Thus, for the preservers the doctrine to lose themselves to the desires of man was to the Old Man of the Mountain all the more a sacrilege against Allah.

Namely, the corruption of the sect’s leader, the current Old Man of the Mountain, would mean the decay of the sect. Whether that leader suffered from a corrupt spirit or declining skills, such a person must not bear the name of the Old Man of the Mountain. To decline was to die. He took their heads in forgiveness of their sin, and passed down hope to the next Old Man of the Mountain.

He chose to fight head-on with a greatsword rather than hidden weapons, in honor of his solemn duty to assassinate assassins. To lay eyes upon his skull mask meant that one’s life was over. After bringing the hammer down upon fools who strayed from the doctrine of the order, the skull-masked swordsman would erase anyone who had witnessed him from the world.

It is said that he, who sent many Assassins to oblivion, remained in the shadows until the destruction of the assassin order. The skull-masked swordsman was a living legend, the abyss of assassins, whom no one has ever witnessed.

He is given the nickname of "King Hassan" (キングハサン) by the Protagonist of Fate/Grand Order. In the 6th Singularity, it is given that he resides within the Holy Shrine of Azrael (アズライールの聖廟), a mausoleum situated in a mountainous region somewhere to the north of Jerusalem.

Appearance
An assassin wearing a skull mask.

Personality
The Old Man of the Mountain comes off as quite the stern and straight-forward individual. He possesses extremely low tolerance for impoliteness, as he almost immediately annihilated the protagonist's group upon their uninvited visit to his temple.

However, he is far from being heartless, simply a man with unshakable faith and strict code of conduct. He was willing to hear his visitor's plea for aid and accept it, but only on the condition that one of the Hassans be willing to die for it.

In his view, for a Hassan to plea for aid, even from their own kind is a grave dishonor to their name and faith, as they are those who must rely on their own individual strengths to preserve through trials and slay their targets. Any Hassan who grows weak and/or becomes reliant on the strengths of others must be dealt with by his blade.

Camelot: The Holy Domain of the Round Table
Approaching the confrontation between the protagonists and the knights of Camelot, the Hashashin attempt to request aid from the Old Man of the Mountain, who is reputed to conceal himself at the Holy Shrine of Azrael.

Upon approaching the shrine, the Old Man of the Mountain puts forth trials to test the characters of the protagonists and the gathered Hassan. Informing the protagonists thereafter that requesting his aid was equivalent in meaning to forfeiting the life of the Hassan of the current generation (Hassan of the Cursed Arm), he relents from enacting his customary cost on account of the circumstances of the Singularity.

Subsequently, he lends the protagonists his assistance during the siege upon the Holy City of Camelot.

Babylonia: The Absolute Frontline in the War Against the Demonic Beasts
Initially taking the appearance of an old, bearded vagrant and assuming the name of (the hero of the Sumerian ), he awaits the protagonist in the city of Uruk -- apparently to again test the protagonist's character. Subsequently, during the protagonists' exploratory mission to the abandoned city of Cuthah, he intervenes when the protagonist's soul is drawn into the Underworld by Ereshkigal.

"You who cannot die -- cannot be said to have ever lived."

- the Old Man of the Mountain, to Tiamat In the finale of the Singularity, the protagonists are able to temporarily trap Tiamat within the Underworld by the assistance of Ereshkigal and Ishtar -- aiming to utilize the Anti-Divinity property of the territory of the Underworld to weaken her. In the midst of Tiamat's attempt to escape to the surface, the Old Man of the Mountain intervenes by slicing off Tiamat's wings and imposing the Concept of Mortality upon her -- stating to the protagonists that he has removed himself of the title of "Grand Assassin" for the opportunity to strike against an Evil of Man. He participates as a guest in the second-to-final confrontation with Tiamat.

Abilities
Differing from his successors, the Old Man of the Mountain terminates his targets not by imposing physical harm, but by severing 'fate' itself by way of an ability similar to the Mystic Eyes of Death Perception.

As with Shiki Ryougi, the Old Man of the Mountain exercises his abilities by the use of a sword. In terms of skill in swordplay, he is said to be more than a match for the knights of Camelot; able to duel with Gawain while holding the advantage and capable of blocking a strike from Excalibur Galatine with his cape alone, he is capable of creating sandstorms at will and eliminating abstract concepts such as communications with Chaldea or Ereshkigal's alliance with the goddesses opposed to Babylonia. He is furthermore capable of imposing "the concept of death" upon immortal existences such as Tiamat. He has shown usage of blue flames to move in manners akin to teleportation, such as moving behind or above targets, or strike his opponents with multiple strikes in a single swing and creating explosions from a distance.

The Old Man of the Mountain is currently the only Hassan without a known Noble Phantasm dubbed with the name Zabaniya. His currently revealed Noble Phantasm is known as Azrael. His personal skills are Battle Continuation and Protection of the Faith.

Presence Concealment
Presence Concealment is the Skill to erase one’s own presence. It is the vestige of an ability he learned long ago. The swordsman bears a powerful curse which makes his presence known those whom he will kill next, even if he achieves a perfect success on a check to conceal himself.

Evening Bell
The Evening Bell (晩鐘) signals the announcement of funereal proceedings and the visitation of Death. This unique skill manifests as a result of having become one with the rites of passing. The swordsman of the Evening Bell is without agency in his choice of opponents. He brings salvation to those who have lost sight of their mortality in the place of God.

"…Canst thou hear this bell? It tolls for thy destiny’s end. Accept it, and unbind thy soul, for this is thy last chance as a human to slumber in peace"

- King Hassan