To consider, or dismiss, as you choose, and in the delusion that today's Google and forum search not locating anything on this subject was actually meaningful and that there aren't already examples out there officially or otherwise.
The Oath of Inquisitorial Service, as sworn by all new members and with each new promotion.
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I swear my life, soul, and duty to the everlasting glory to the God-Emperor of all Mankind, and his Inquisition.
I will war forever upon the heretic, the xenos, and daemon, always unmerciful, never yielding. My fellow crusaders I call upon to slay me should I fall under dark sway.
Only the God-Emperor's hand may stay us in our purpose.
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It's simple and to the point.