What is the opposite of a shill?

Question

I’m looking for a single word (or at least a short term) that is the opposite of “shill.”

Let me provide some context for what I intend to mean by shill:
In situations where someone is presenting something to a crowd of neutral onlookers (this can include on the internet), either selling something or presenting an idea, a “shill” is a person who is part of the con or has been paid off ahead of time, and pretends to be one of those unassociated onlookers but to act really impressed (“That’s so cool! I’ll buy one!” or “I totally agree!”). The idea is to get other people to go along using crowd psychology.

Now when I say the “opposite of a shill,” I mean a person who similarly pretends not to be associated with the presenter, but has been paid off to act as an ANTAGONIST.

This can be as mild as playing devil’s advocate, where they just question the presenter, who in turn answers them with fancy pre-written answers. But I mean where it is more insidious, where they play the villain to the extreme. This can include things like making counter-arguments to the presenter but deliberately using very poor reasoning, and/or extreme language and dogma to make the presenter’s opponents look foolish or vicious. I even heard of a case where a group of political protesters arranged for a small group of people to “counter-protest,” throw eggs at them and shout slurs at them to make them look like martyrs.

So, is there a recognized word for this? Or can “shill” include this meaning?

Answer 1

that would be "llihs".

Answer 2

shill - noun: a decoy who acts as an enthusiastic customer in order to stimulate the participation of others

another word might be "plant"
noun: an actor situated in the audience whose acting is rehearsed but seems spontaneous to the audience

Answer 3

Sorry, only thing I can come up with is "Customer"... chuckle

Answer 4

'Mark', 'sucker'.