What's a word for "causing conflict/inciting hostility/setting people up against another/enciting violence"

I'm sure it's an easy word that's just trapped in the back of my mind somewhere, but google didn't help, so I hope you guys can.

When someone has been conniving and conspiring to meddle in the affairs of other people behind their backs, and set formerly friendly people or parties up to be hostile towards one another, then that person is... ?

"They were as suscpetible to his ___" (not 'meddling', but specifically causing hostility and turning relations sour)

The closest candidates I can think of are 'pulling strings' and 'shit stirring'. Maybe the word could also be used to describe the action of a dog owner inciting his dog to go for another person or game.

Thanks for any help and all effort.

Instigate, Incite/Incitement, goad fit the purpose well.

Invidious or maybe an invidious interloper, or invidious intent.

Google Dictionary definition