Untold ages ago, an immense crisis struck specific galaxies in Earth-One's universe. The Guardians extracted malignant energies from their dimension, concentrating them and transporting them into a solar body in Earth-Two's universe known as the Starheart. They then combined their own mental energies into a device on the planet Oa known as the Central Power Battery. From this battery, first the Guardian's android Manhunter agents followed by the Green Lantern Corps used portable power batteries to access the emerald energy emanating from the Oans. Meanwhile, the combined energies in Earth-Two created a sentience known as the Green Flame of Life... which corresponded to the Green Glob of Earth-One. While the Malthusians of planet Malthus, from which the Oans originated, had counterparts in Earth-Two's universe of the Buddak, this race was malevolent. Hence, the Buddaks didn't enlist the aid of a Green Lantern Corps as did their Guardian counterparts, although the Green Flame meteorite would empower several residents of Earth-Two including Chang and his Green Dragon Tong and the future Green Lantern, Alan Scott.
That same Green Flame was the source of Chang's immortality throughout the centuries. Lord Chang, a lamp maker who formed from the Starheart's meteorite a lantern that would one day be passed down to Scott... only gained similiar powers to that of the Emerald Crusader when Green Lantern temporarily turned evil under Psycho-Pirate's influence. And while Alan faced certain danger from Chang, his Justice Society ally the Spectre also faced a similar threat from Chang's fellow immortal Shahn-Zi, the Lord of the Yellow River. Combating the former JSA member and Earth-One's Batman, Shahn-Zi had like Chang ultimately lost his life when both attempted to conquer their respective Gotham Cities. As for the Central Power Battery, it was temporarily transferred to Earth-Two, while the Starheart ended up stolen by Zalaz and returned to Earth-One's cosmos where it was consumed by M'la. This would be offset by the addition of a third power battery, that originating from Earth-Three's cosmos in another tale.