Is it possible to sue the agent acting on behalf of someone even if it can't be proven if that person exists

Question

What I mean is, if there are one or more people, or agents, behaving in a way or doing something wrong that causes harm to come to others (harm being very broad in scope) and

1) the agents are acting on the behalf of, or are representing a higher authority or party, yet
2) it cannot be proven that that authority or party truly exists or
3) it cannot be proven that the authority actually instructed the agents in how to act,

can a suit or indictment be carried out against either the agents, the unknown party, or both?

Answer 1

Criminally, Charles Manson was held responsible for instructing others to commit murder... so you'd be adding on someone instructing him... by precedent.

You could sue the agent for doing something unlawful, but you could not sue an unknown and unprovable entity.

Answer 2

you are gonna have to be able to proove something.
if you sue said agent then you need to have proof they are acting as agent.
if you sue the party directly then the party must in fact exist.
you need something concrete

Answer 3

you sue the agent, period. If the agent does not want to assume liability they have to disclose their principal (boss).