Most companies limit reference checks to employment dates, title verification, and eligible for rehire only. Most places have policies that limit the info given andvrequire only HR to speak to prospective employets. Not saying that applies in your case, but that is the general climate.

I guess too bad for an employee who happens to have a total asshole/mentally unstable manager who hates them just because.

You would have no recourse if the manager speaks the truth. If the manager were to lie about you that would be actionable slander.

Most likely your employer will only receive a confirmation of employment from such and such date to such and such date.

But, you can't sue just because someone bad mouths you.

That depends. Why do you suspect your current manager will give you a bad reference?

I am currently looking for a new job. I do not expect that my current manager will give me a good reference. I have plenty of other great references from a long and successful work history. What if a future employer requires that they speak with this particular manager? What type of recourse would I have (if any) if I were to discover that this manager has spoken negatively about me? Granted, I will not give this manager's name and contact information unless I absolutely have to, but in the odd circumstance where I might have to, what rights do I have?