Most employment contracts state that what you make during work time belongs to them. Read what you signed then get a lawyer.

Any retribution will be illegal and may find yourself in hot water.

Did they promised you something and didn't deliver?

OR

You think you deserve to get something from someone else and didn't get what you wanted?

These are two different things. If it is latter - move on and succeed elsewhere.

Publish an anonymous blog detailing everything and then send the details out to all the news sources you can find?

Before anything else: lawyer up

What about competitors ? If this is important enough for a patent filing, there may be competitors to your ex-firm interested in your skills and expertise. Have you considered that angle ?

Country - India