Executor

Executor
Inquisitors of the Holy Church. Those who eliminate heresies that do not exist in the Church's doctrine.
What makes them different from exorcists is that they do not exorcize demons, but eliminate them.
For a more detailed explanation, consult the latter half of the Sakura route.

Fate/side material: Fate Encyclopedia
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Inquisitors of the Holy Church. Those who eliminate heresies that do not exist in the Church's doctrine.
What makes them different from exorcists is that they do not exorcize demons, but eliminate them. If exorcists are those who drive out devils from the possessed, then executors are those who exterminate devils on the spot. Not banishing, but defeating; not rescuing, but erasing. They are more like professional killers than priests.
However, according to the Church, humans do not have the authority to defeat demons, because even demons are the creations of God. The name “executor” comes from the fact that the executors transcend that teaching, and act as God's proxy on earth to stamp out heresy. They are an army of believers, devised of by the 120 Cardinals supporting the Pope. It wouldn't be a mistake to call them the Church's greatest treasure.

Tsukihime Dokuhon Plus Period: Tsukihime Dictionary Revised
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Inquisitors of the Holy Church. Those who eliminate heresies that do not exist in the Church's doctrine.
If exorcists are those who drive out devils from the possessed, then executors are those who exterminate devils on the spot. “Not to banish, but defeat. Not to rescue, but erase.” That is the ideology that drives the executors.
However, according to the Church, humans do not have the authority to defeat demons, because even demons are the creations of God. The name “executor” comes from the fact that the executors transcend that teaching, and act as God's proxy on earth to stamp out heresy.

MB Act Cadenza PS2 Manual: Tsukihime Dictionary
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executor