Kayneth's Servant in the 4th Holy Grail War. Honorable and lives for the fight while fights with his dual spear-wielding style.
In his past life, Lancer was Diarmuid Ua Duibhne, an Irish warrior part of the mythical Knights of Fianna. He is known under the name "Diarmuid of the Love Spot" because of a magical love spot on his face given to him by a young girl that makes any woman gazing upon it to fall in love with him. This love spot led to Diarmuid's encounter with Grainne, the bride of one of his fellow Knights of Fianna named Fionn mac Cumhaill. Falling for Diarmuid, Grainne placed a curse on the knight to force him into fleeing with her. This led the two to be relentlessly persued by Fionn. But after enough bloodshed from Fionn's failed efforts, he was forced to acknowledge the pairing between the two, restores Diarmuid's status among the knights and gives him land.
Some time later during a hunting trip with Fionn, Diarmuid would be fatally injured by the fangs of a wild boar. While Fionn had the ability to transform a nearby spring of water into a powerful healing agent, his jealousy of Diarmund led him to intentionally neglect the man's wounds until he succumbed to death.
Lancer is created by Gen Urobuchi and designed by Takashi Takeuchi as one of the supporting character for the Fate Zero anime series. He originally appears in the visual Fate Zero, and makes his first anime debut in Fate Zero episode 3, the Land of Fuyuki. He is voiced by Hikaru Midorikawa.
Lancer stands at 6 feet tall and wears a dark teal outfit while in battle. He is an attractive man with long, rough hair.
Lancer is an honorable and loyal knight who is willing to follow the orders of his lord and follows a personal code of honor that he follows when engaging in battle with others, earning him the respect of Heroic Spirits like Saber and Iskander.
Lancer was summoned into the 4th Holy Grail War by Kayneth Archibald El-Melloi when his means of summoning Iskander were stolen by one of his students, Waver Velvet. The circumstances of Lancer's summon are unique in the fact that Kayneth holds the Command Spells used to order him and Kayneth's fiancee, Sola-Ui, is used to supply mana to him. Kayneth would have Lancer openly make his location known to get the attention of other Masters and Servants competing in the Grail War while he would keep hidden from the area in which they fight.
Lancer's first opponent would be Saber. Upon getting an upper hand on his foe through use of Gae Buidhe, their fight would be interrupted by the appearances of Iskander, Berserker and Gilgamesh. Kayneth tries to get Lancer to team up with Berserker against Saber, but the latter's personal honor would forbid him from doing so and he is forced to do so with a Command Spell. Realizing this, Iskander forces Kayneth to have Lancer retreat lest he team up with Saber to kill Lancer off.
A disgusted Kayneth would berate Lancer later on for his disobedience and begins to suspect that his Servant might be having an affair with Sola-Ui. Before the matter could be discussed though, Kayneth's hideout at a hotel would be attacked by Kiritsugu and Maiya who used bombs to destroy the hotel's foundation and cause the building to collapse.
Lancer would later aid Saber in dealing with the familiars summoned through Caster's spellbook and come to Kayneth's defense when he gets crippled through Kiritsugu's attack. Sola-Ui would then force a bedridden Kayneth to give up his Command Spells and become Lancer's Master. To Lancer's horror, he realizes that his love spot has caused Sola-Ui to fall madly in love with him and regrets that he may be repeating the same tragic events that occurred through his time alive. Lancer would team up with Saber and Iskander later on when confronted with Caster's massive monster as he willingly destroys Gae Buidhe to allow Saber full use of her abilities to defeat Caster.
Saber and Lancer meet again to settle their battle from days earlier with Saber choosing to simulate the injury she gained from Gae Buidhe out of honor for her opponent. Unbeknowst to the two of them though, Kiritsugu had set up a plan to lead to Lancer's death by forcing Kayneth to command Lancer to kill himself through a Command Spell while holding Sola-Ui as a hostage. Enraged with the similar circumstances in which he dies a second time, Lancer curses Saber, Kiritsugu, the Holy Grail and the world for his fate as he vanishes.
Lancer is a very skilled spearman capable of wielding two spears in battle and is one of the fastest Servants competing in the Grail War. Being calm and perceptive in nearly all instances he fights thanks to his Eye of the Mind (True) skill, Lancer is a clever tactician who is able to calmly analyze the abilities of his foes and make use of his weapons and environment to his advantage if he knows he has any chance of victory. This was demonstrated in his first fight with Saber where he set up a clever trap that fooled Saber's instincts into falling for an attack from Gae Buidhe.
The Noble Phantasms that Lancer uses in battle are his two spears, Gae Buidhe and Gae Dearg. With Gae Buidhe, any wound inflicted on its target is incapable of being healed through any natural or magical means unless the spear or its owner are destroyed. Gae Dearg is capable of shutting down any magical enhancements and projections used by its foe by severing all their ties with the mana of its owner.