instigator:
(plural: ‘instigators‘; pronunciation: the letters ‘i’ rhyme with the letter ‘i’ in “ink” — for the right pronunciation of this word, please click here)
a person who starts something (usually something bad or dangerous) to happen by his actions;
a person who causes someone to act, usually wrongly, especially by forceful speech or by giving wrong information or facts (instigators usually cause riots, political disturbance, workers’ protests in a factory or company),

a political instigator instigating the crowd through his speech
When we were kids, my elder sister used to be the instigator for all the trouble at home… encouraging me and my younger sister to do all sorts of nasty things and get the blame!
Behind every riot or arson there is bound to be an instigator, motivated by political or religious beliefs.
Though ‘instigator’ is most often used in the negative sense, there are occasions where this word is used in the positive sense, mostly to mean ‘inspiration’ and ‘influence’ to get positive results.
The police are looking for the instigators, three senior students, who allegedly instigated their juniors to deface the founder’s statues on the college premises.
