Berserker (Fate/Irregular)

Fenrir is a Berserker class Servant.

Identity
Fenrir (ヒーンレル; Hinreru), also known as Sköll, Mánagamr, or Háti, is the great wolf of Norse mythology. He was one of the progenies of the trickster god Loki. Fenrir was regarded a threat to stability of the Nine Worlds as he grew up, causing the Aesir gods to decide to restrain him for the safety of the universe.

The gods attempted to restrain Fenrir, under the guise of a game to test his strength, twice and failed both times. A third attempt was performed with the strongest chains that the dwarves were able to forge. However, Fenrir was suspicious of this third "test," demanding that one of the gods hold a hand in Fenrir's mouth as a gesture of good will. Only Tyr had the bravery to offer his hand, knowing the outcome. When Fenrir was bound and unable to escape, he tore Tyr's hand from his arm in retaliation. Fenrir was chained to a boulder and a sword shoved into his mouth to keep his jaws open.

But even the greatest chains are not enough to hold Fenrir forever. In his rampage during Ragnarok, Fenrir killed Odin, the All-Father, and consumed the sun and moon before being struck down in vengeance by one of Odin's sons.

Personality
As Berserker, Fenrir possesses little speech, but he is not completely speechless. Since he spent much of his life desiring revenge for being locked away, he had grown accustomed to the rage induced by the Berserker class.

Abilities
Fenrir is a strong competitor as one of the strongest Heroic Spirits ever summoned as a Berserker. Easily equal to Heracles in strength, Fenrir is difficult to restrain and possesses a regenerative factor that enables him to, given enough time, shrug off even the heaviest of blows.

Fenrir's greatest power is his sense of smell. With it, he is capable of sensing even Assassin, within a radius equal to a city block. At greater distances, Fenrir loses his ability to pinpoint enemies, but retains an idea of the general direction, provided that the environment is not redirecting the scent.

Fenrir's ultimate Noble Phantasm is Ragnarök. It creates a reality marble where neither the sun nor moon exists, producing a realm of darkness and coldness. Unaffected by these side effects, Fenrir is free to prey on all of his enemies within the marble to his liking while his victims are unable to see and gradually lose their ability to fight back in the extreme cold. The fact that Berserker classes typically are incapable of producing reality marbles only accentuates the threat that Fenrir posed as a servant.