What do you call somebody who brings forth change?

Looking for a word for a body or group of people who are the initial/prominent cause of a change. For some reason my mind keeps going to angels in the bible? I think there may be a phrase used to describe angels as some kind of bringer forth of change or judgment. Unsure. The _____ of change.

Please help. My mind is drawing a blank and I've been googling for 15 minutes and have found nothing.

The word that comes to my mind is harbinger:

one that initiates a major change : a person or thing that originates or helps open up a new activity, method, or technology : PIONEER

It has a literary feel to it and was used (in the “messenger” sense) in at least one translation of the Bible.

I have always used the word catalyst:

2 : an agent that provokes or speeds significant change or action
// That waterway became the catalyst of the area's industrialization.
// He was the catalyst in the native uprising.

In your sentence:

The catalyst of change.