Lancer, known in Portuguese as Lanceiro and whose true name is Cú Chulainn, is a Servant of the Lancer class who participates in the Fifth Holy Grail War as depicted in Fate/stay night. He originates from Celtic mythology, specifically the Ulster Cycle, as the demigod son of the sun god Lugh and a mortal woman, and is famously known as the Child of Light. In the story, his original Master was Bazett Fraga McRemitz, but before the war begins, the priest Kirei Kotomine attacks and kills her, stealing her Command Spells and forcibly assuming control over Lancer. This coerced contract creates a relationship built on distrust, as Lancer fundamentally despises treachery and underhanded methods. He values straightforwardness, loyalty, and personal honor above all else. In personality, Lancer presents a playful and carefree demeanor, enjoying life with an easygoing attitude, but this shifts dramatically in combat, where he becomes intensely focused and passionate, working himself into a battle frenzy. He craves worthy opponents and relishes genuine, life-or-death clashes. His core motivation is not a wish for the Holy Grail but rather the desire to fight a truly satisfying battle against a strong adversary. His role in the narrative is multifaceted. He is the first hostile Servant encountered, tasked by Kotomine with reconnaissance and harassment rather than outright victory. This restriction, enforced by Command Spells, prevents him from fighting at full strength for most of the story. Across the three routes of Fate/stay night, his position shifts from antagonist to temporary ally, and his fate varies tragically. In the Fate route, he engages in a prolonged, evenly matched duel with Gilgamesh but is ultimately killed by him. In Unlimited Blade Works, Kotomine forces him to commit suicide via Command Spell, yet Lancer, with immense willpower, survives long enough to impale Kotomine from behind and set the Einzbern castle ablaze with rune magic before dying. In Heaven's Feel, he is ambushed and killed by True Assassin while distracted by the shadow of Sakura Matou, and his heart is consumed, granting the Assassin enhanced intelligence. Key relationships include his adversarial yet respectful dynamic with Saber, representing opposing ideals of knighthood, and his grudging, temporary alliances with Rin Tohsaka and Shirou Emiya when their goals align against common threats like Caster or Archer. Regarding abilities, Lancer embodies the agility-focused Lancer class, standing approximately 185 centimeters tall and weighing 70 kilograms. His combat style relies on exceptional speed, agility, and masterful spear techniques. He is also highly proficient in rune magic, having mastered the original eighteen runes, which he can use for elemental attacks, parameter enhancement, and even nullifying magical eyes, though he prefers direct physical combat over spellcasting. His defining Noble Phantasm is Gáe Bolg, a cursed crimson spear that possesses two modes. The first is a barbed thrust that reverses causality, ensuring the spear strikes the heart before the attack is launched, making it nearly unavoidable unless the target possesses extraordinary luck. The second is a thrown version that functions as an explosive anti-army projectile with immense destructive force. Throughout the story, Lancer remains a figure of honor and tragic fate, caught between his own warrior code and the manipulations of his Master, ultimately demonstrating unwavering resolve and a fierce loyalty to his principles until his final moments.