Dan Blackmore is a former military officer from England who serves as a Master in the Moon Holy Grail War, participating as a representative of the Western European plutocracy. He is an elderly man of sixty years, standing at 166 centimeters tall with a lean, well-trained physique. His appearance is that of a distinguished gentleman with pure white, grayish hair and a face deeply marked by age. However, these signs of aging do not convey frailty; rather, they are likened to the rings of a tree, where his many scars have become a solid core and tough bark, making it impossible to see his years as a weakness.

Blackmore is a decorated veteran and a renowned sniper from his youth, having been bestowed the title of knight by the Queen of England. He hails from an old family with magical circuits, which he personally detests, but he was unable to refuse the Queen's request. Fearing that the Harwey family would monopolize the Moon Cell, the Queen sent him as her most trusted private soldier. After training and adjustment, he became a Spiritron Hacker. His life has been marked by loss, having lost his wife Anne and his ideals on the battlefield, which led him to see the Holy Grail War as his final opportunity to fight as a knight.

In terms of personality, Dan Blackmore is a serious, polite, and respectful individual who strongly adheres to a code of chivalry. He believes in facing opponents in honorable, direct combat and disapproves of cowardly tactics. His servant is the green-clad Archer, whose true name is Robin Hood. This creates a significant point of contention between them, as Blackmore constantly restrains his servant from using guerrilla warfare, poison, traps, and surprise attacks, even going so far as to use a Command Spell to forbid him from using such methods. He believes the Holy Grail War is a contest where one should fight fairly, a stark contrast to Robin Hood's pragmatic and stealth-based approach to survival.

Blackmore's primary motivation for entering the war is deeply personal. While he officially participates on behalf of the Queen, he admits that his true wish is to use the Holy Grail to revive his deceased wife. He carries immense regret over his life as a soldier, feeling he sacrificed his personal life for duty. Upon his defeat, he realizes the potential selfishness of this wish and admits to being confused about whether he truly wants his wife back or merely to return to the person he was before becoming a soldier. He is a man who has spent his life suppressing his feelings for the sake of being a good soldier, and he sees the war as a chance to finally fight for a personal goal.

In the story of Fate/Extra Last Encore, Dan Blackmore appears as the Floor Master of the second stratum. After being defeated in the original Holy Grail War a thousand years prior, he was resurrected by the Moon Cell following a world-altering event. However, as the dead cannot be restored to their true selves by a system that rejects emotion, Dan has changed drastically over the millennium. The chivalrous knight has been reduced to a ghost driven solely by a blind pursuit of victory. He becomes a ruthless hunter who, alongside his servant Robin Hood, has killed countless Masters and Servants who tried to ascend the second floor, despite the fact that, as a defeated spirit, he is incapable of ever progressing to the third floor himself.

As a Floor Master, he is a formidable opponent who relies on a meticulously crafted three-part trap honed over a thousand years. His strategy begins by sniping Masters as soon as they emerge from the ladder to his floor, using a ricochet effect off the bells of a clock tower to mislead them into believing he is hiding there. Those who survive and flee into the forest are then hunted by Robin Hood using poison fog and traps. Finally, if an opponent manages to survive both the sniper and the forest, they are drawn to the clock tower, which they assume is the sniper's nest. Dan is not there; instead, the tower is a dummy packed with explosives. This brutal efficiency showcases his transformation from a chivalrous soldier into a machine of war.

Key relationships for Dan Blackmore center on his bond with his servant, Robin Hood. While they constantly clash over tactics, with Dan scolding Robin Hood for his dishonorable ways and Robin Hood complaining about his master's stubbornness, a deep, almost father-son bond exists between them. In their final moments in the original war, Dan apologizes to Robin Hood for restricting his fighting style, and Robin Hood thanks him for allowing him to feel like a hero for once. Robin Hood remains loyal to Dan even after his transformation into a Floor Master, continuing to fight by his side for nearly a thousand years and keeping from him the fact that, as a loser, he can never ascend. Blackmore also serves as a mentor-like figure to the protagonist, Hakuno Kishinami. He offers guidance on the nature of fighting and the weight of one's choices, teaching that one must not turn away from regret or the consequences of their actions but instead use them as fuel to move forward.

Blackmore's development is most evident in the contrast between his original self and his corrupted form in Last Encore. In his original life, he was a man torn between duty, honor, and personal grief, seeking a wish but also a dignified end to his life as a knight. After a thousand years as a Floor Master, most of that humanity has been stripped away, leaving only a spirit of bitter victory and a tactical, almost robotic, adherence to killing. However, in his final defeat, a flicker of his old self returns. As he lies dying, he hears the ringing of the bells and has a brief, peaceful memory of his past life and his wife before fading away, finally finding release. His notable abilities are those of a master sniper, capable of crawling for a kilometer and precisely eliminating a target. He is a tactical genius who uses the environment to his advantage, setting up elaborate kill zones that exploit the psychology of his prey.