Twice H. Pieceman is the Master of Savior, and the primary antagonist of Fate/Extra. At the conclusion of the seventh battle, he can be found at the core of the Moon Cell.
Twice H. Pieceman is in his late 20's with black hair and grey eyes and wears glasses. He wears doctor uniform with black collar long sleeves white shirt with black, grey, and light blue tie and grey sweater vest, white lab coat, black gloves, black pants with grey lines, and black shoes.
Twice H. Pieceman was a prominent scientist in the latter half of the 20th century, and pioneered the science of digital hacking. Killed in the terrorist attack occurring some thirty years prior, his data was recorded by the Moon Cell Automaton and became part of the system. Though a pacifist by nature, his constant exposure to war and the evils of mankind caused him to develop a mental illness. Twice hates war and cannot forgive it, but at the same time believes that humanity requires war to advance and evolve. This dissonance caused his data to become self-aware, and now exists in the Moon Cell as an NPC. To him, the Holy Grail War existing within the Moon Cell is a microcosm of the constant bloodshed that transpires in the outside world. The participants slaughter one another in the hopes of having the Grail grant their wish, all the while feeding information to the Automaton. Pieceman accepts this as survival of the fittest and believes that such a process is essential for humanity.
After becoming self-aware, Twice became a Master and summoned Caster and fought in countless Holy Grail Wars, but failed to win the war until he summoned Savior. However, once reaching the core of the Moon Cell, he found that, as an NPC, he could not enter the core without being deleted. From there, he redesigned the Holy Grail War to the current system and asked each Master who was victorious in the Holy Grail War to wish for the perpetuation of war and the continued advancement of man. However, all the Masters who faced him refused, and thus were killed by him and Savior.
When the main character and their Servant reaches the core, he makes the same request, unaware that they are an NPC as well and likewise cannot enter the core without being deleted. The main character and their Servant reject Twice's philosophy and do battle with him and Savior. After Savior is defeated, Twice deletes himself, staying true to his beliefs about survival of the fittest.