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. It is an infinite energy source that provides incredible power output and excellent mobility.

Mega Man 2: The Power Fighters
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 which he named Bassnium, he then created a powerful robot to use this energy. At the time of the classic series, Bassnium was the most powerful energy in the world. Dr. Wily later tells Bass about his discovery of Bassnium, and how he is studying this energy to create a new powerful robot.