A person who tries to stir up people in support of a cause
someone who deliberately foments trouble
Calm is defined as a state of peace and tranquility.
Something different; variety:
Find another word for instigator. In this page you can discover 13 synonyms, antonyms, idiomatic expressions, and related words for instigator, like: agitator, fomenter, inciter, initiator, provoker, instigant, firebrand, ringleader, calm, change and politics.