During his confrontation with Kiritsugu Emiya, Lancer, Diarmuid Ua Duibhne, was forced to commit suicide with a Command Spell. It turned out that Kirei Kotomine had given Kenessis a Command Spell after Lancer eliminated Caster, and Kenessis had killed Kirei Kotomine. Kiritsugu threatened Kenessis with his fiancée's life, forcing Lancer to commit suicide, and they signed a contract that Kiritsugu would not harm Kenessis or Soula. Lancer, enraged, lamented the betrayal and questioned the desperate pursuit of the Holy Grail.
With the Holy Grail appearing before Lancer, he was revived, and Lancer faced off against Lancer in a final duel. Lancer, filled with gratitude, accepted the challenge, and after a brief exchange, Lancer was defeated. As Lancer fell, Artoria Pendragon questioned the nature of the Holy Grail, only to be told by Lancer that it was merely a powerful magical core, a tool for mages to reach the Root and recreate the Third Magic, using the souls of Servants as a conduit. The Grail, Lancer explained, was not a means to save Britain.