Assassin (Fate/Grand Order - King Hassan)

Assassin (アサシン) is an Assassin-class Servant appearing 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, but it is unknown if this was permanent.

Identity
Assassin's True Name is Hassan-i-Sabbah, the founder of the Hashashin, who became the first to take upon himself the title of "the Old Man of the Mountain" (山の翁), and the name 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 were the sect to persist in righteous accordance to the doctrine of Allah, it was inevitable that those avowed carry it forth might sin -- but for the preservers the doctrine to lose themselves to the desires of man was to the Old Man of the Mountain the gravest of sins.

To him, the rot and the corruption of the sect were equivalent in meaning to the waning of its leader. Whether by the waning of spirit or the waning of skills, one upon the threshold of decline could no longer be seen as fit to hold the title of "the Old Man of the Mountain." The sin of degeneration could be answered only by beheading -- such that the hopes of the sect could be entrusted to a successor.

He who assassinates the assassin -- who enacts the carriage of justice against those would stray from the doctrine of the sect -- chooses not to employ an assassin's tools of trade; he approaches openly and without deceit, carrying only a broadsword. Should a man come to glimpse the skulled swordsman, his existence is as good as concluded.

Unto the end of the Hashashin, the skulled swordsman concealed himself within the shadow of the sect; persisting as the very Abyss (暗殺者の深淵) -- a living legend in the absence of a single witness.

He is given the nickname of "King Hassan" (キングハサン) by the Protagonist. In the 6th Singularity of Fate/Grand Order, 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.

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
Posing initially as [Ziusudra], he approaches the protagonist during their stay within the city of Uruk.

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; readily defeating Gawain and blocking the 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.

The Old Man of the Mountain is the only Hassan with a Noble Phantasm not dubbed with the name Zabaniya.

Personal Skills
His personal skills are Battle Continuation EX, Protection of the Faith A+++, and Evening Bell EX.

Presence Concealment
Presence Concealment (気配遮断), Rank A -- the capacity to eliminate one's presence. Effectively, the remains of a skill acquired long ago. Being that the skillholder is a swordsman who bears a powerful curse, even if an attempt at the concealment of presence is essentially flawless, any target he intends to kill would be able to discover his presence.

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.

―Dost thou hearest the tolling of the bells? This is the end of thine destiny. Accept it and free thy soul. That is the final chance to rest as a human.