Is there any way for me to take legal action against my former boss for wrongful termination, and/or deformation even though Maryland is an at will state?

Sure, sue them in civil court. But do your research. Is it worth your time and money to do so?

At will means they can fire you for any reason but if you take them to court they MAY need to have a pretty good reason why.
Defamation? Of character
Depends on things like if it was true or not and what damage it cost you... like your job and what else?

Look for an employment law attorney in your area.

Do you feel you were discriminated against? What is your claim of wrongful termination? For the right reasons, you can file a claim on your own with the EEOC. An employment law attorney will often review your case and possibly assist on a contingency basis - not paid unless you win your case.

It is worth pursuing if you have a very strong case and can show that you suffered considerable damages. Unless your damages (money lost) are great enough to both pay you and your attorney handsomely, you will have to pay up front for an attorney. They typically will only take cases on a contingency basis (they get paid when they win a settlement) if you are out a lot of money.

It's worth calling a few lawyers and seeing what they say. Usually though, you're better off just moving on and finding another job. Unfortunately while the laws protect you, to enforce those laws can be very difficult and costly.