DictionaryinstigatorPerson who prompts action
noun

instigator

IN-stih-gay-ter/ˈɪnstɪɡeɪtər/

A person who starts or provokes an action or event.

The instigator hands another spectator a tomato and points toward the performer.

An audience member incites a hostile disruption of a performance: he supplies a tomato to another spectator and emphatically points toward the performer as she raises another tomato to throw.
Etymology

Latin instigator meant “a stimulator,” someone who urges action. This makes an instigator the person who sets trouble in motion, including by encouraging others to act.

In context

Moxie Institute | Fia Fasbinder CEO & Speaker2:31
you are both a moderator and an instigator meaning you will start the fires but you'll also put the fires out you will ask the questions to steer the conversation in the right direction
How To Moderate A Panel Discussion Audiences Will Love | Media Training

More examples

  • The principal asks who was the instigator of the fight.
  • Maya is the main instigator behind our neighborhood cleanup.
  • The instigators of the walkout urge their coworkers to join.

Forms

instigator · instigators

instigate verb — To start or provoke an action.

instigation noun — The act of starting or provoking something.

Similar words

initiator
Starts an activity without necessarily provoking conflict or trouble.
provocateur
Deliberately provokes strong reactions, often for political purposes.
ringleader
Leads a group engaged in mischief or illegal activity.