During the month of October is #Inktober! Each day has a single-word prompt, but instead of inking something, I'll be designing a Magic: The Gathering mechanic to fit the word. This is called #Meltober, named after "Mel", the more mechanically-inclined counterpart to "Vorthos" of the aesthetic profile spectrum.
Today's prompt is "tranquil."
White and blue are very good at maintaining the peace. Blue can counter spells to keep them from resolving, both blue and white tap down creatures (and detain them, which makes maintaining the peace backwards-compatible with Return to Ravnica's Azorius mechanic), white can destroy attacking creatures without letting any damage end up getting dealt, and white can prevent or redirect damage (though, you'll need to avoid those white combat tricks that deal damage in order to maintain the peace).
I like the idea of a zealot of peace, someone who fanatically wants no trouble to be stirred up. :)