Green Lantern: First Flight

Before any other sentient beings existed in the universe, a race of beings calling themselves the Guardians of the Universe harnessed the power of the green element, the greatest power in the universe, to create the Green Lantern battery. However, the battery was vulnerable to the color yellow, the one part of the light spectrum that could resist green. The Guardians hid the most concentrated source of yellow energy, the yellow element, to prevent others from using it against them.