Found the Final Final Final Boss, The Higlander of Moa birds.

They should change the description text from "Minion" to "Reviving Minion"

I'm on my phone and don't see well but this looks like a minion.

Some rares can have "revives minions" as modifier.

You'll he killing minions for an eternity if you don't kill the rare.

Normally they all come as one pack but I've had experiences like yours where the rare was offscreen and not chasing me. Just trolling with minion revives.

Momma didn’t raise no quitter