I'm sure you know the legend Rin, the Greek hero Heracles had to overcome the twelve labors in order to atone for his sins, and the reward he received was a form of immortality. A curse that forces him to live through the deaths he avoided in life.
~ Illyasviel von Einzbern
Berserker Heracles is a Servant from the visual novel Fate/stay night, developed by Type-Moon.
Berserker is Heracles, the demigod son of Zeus from Greek Mythology. During the Fifth Holy Grail War, where seven mages summon spirits from the past to fight for them in a tournament in hopes on winning the wish-granting Holy Grail, Illyasviel von Einzbern managed to summon Heracles into the Berserker class. While at first he was uncontrollable, Illya and Berserker grew closer once Berserker saved Illya from wolves. Throughout the rest of the Holy Grail War, Illya and Berserker were one of the most dangerous teams, Illya constantly talking about her Servant's invincibility and might.
Mad Enhancement: A skill granted to the Berserker class that boosts their strength at the cost of losing their sanity. Heracles' Mad Enhancement rank is B, ridding him of nearly all rational thought.
God Hand: Twelve Labors: Berserker's main Noble Phantasm, God Hand is a natural ability of Heracles that lets him revive from death twelve times, each time becoming immune to the next thing that killed him. It also cancels out all attacks used on him that are less than A-rank in strength.
Nine Lives: The Shooting Hundred Heads: Berserker's other Noble Phantasm, Nine Lives lets Berserker land nine swift strikes at the speed of sound, the hits going so fast that they appear to be happening at the same time.
Axe-Sword: A massive flint blade made from a column of an Einzbern family temple. With his massive strength, Berserker easily wields the giant sword, and due to its material, it's more like a blunt weapon than an actual sword.
Blackened Berserker: When drenched in the cursed mud of the Holy Grail, Berserker was blackened. While blackened by the mud, Berserker gains a massive power boost due to the grail providing him with mana. However, the blackening makes Berserker completely uncontrollable, as it causes him to go on a destructive rampage.