Bassnium

"Currently Bassnium is the most powerful energy on Earth."

- Dr. Wily

Bassnium, known as Fortenium (フォルテニウム) in Japan, is the energy that powers Bass.

History
Tired of his constant defeats, Dr. Wily began to study Mega Man hoping to create a similar robot, during this process he unintentionally created a powerful energy source which he named Bassnium, he then created Bass using this energy. At the time of the classic series, Bassnium was the most powerful energy in the world.

Mega Man 2: The Power Fighters
After Bass defeats Wily, he tells Bass about his discovery of Bassnium and how he is studying this energy to create a new powerful robot that has more strength than Mega Man and Bass together. Bass responds saying that a "girlie-looking long-haired robot" like that would never defeat him.

Characteristics
Bassnium is an alloy and an infinite energy source that provides incredible power output and excellent mobility. Possibly radioactive in nature.