How would you describe the character of Bach’s Fugue No. 2 in C Minor? What is the main theme a a fugue called?

The character of Bach's Fugue No. 2 in C Minor can be described as intricate, introspective, and emotionally intense. It presents a sense of struggle and tension throughout, with its dark and somber atmosphere.

In a fugue, the main theme is called the "subject." The subject is a melodic idea that is initially presented in one voice and is then imitated by other voices throughout the piece. It serves as the foundation for the entire fugue, with the other voices developing and interacting with this subject in a contrapuntal manner.