Diarmuid Ua Duibhne is the Lancer-class Servant from Fate/Zero, a heroic spirit based on the legendary knight of the Fianna from Irish mythology. Known as the 'First Knight' and 'Beautiful Youth with Two Spears,' he wields the twin Noble Phantasms Gáe Dearg and Gáe Buidhe, red and yellow spears that sever magical energy and inflict incurable wounds. Summoned by Kayneth El-Melloi Archibald, he demonstrates unparalleled loyalty despite his master's flaws. His love spot (Báobh) on his face enchants women, causing tragic romantic entanglements. Diarmuid possesses high parameters: Strength A, Agility A+, and skills like Eye of the Mind (True) and Golden Rule. Noble and tragic, he seeks perfect service in the Holy Grail War.