Three and a half billion years ago a humanoid race from the world of Maltus sought to bring order to the stars. An offshoot of the race became known as the Guardians of the Universe. They sought to remove magic from the universe, and laid siege to the necromantic forces of the cosmos. The war was costly on both sides. The last to fall was the powerful Empire of Tears, finally subdued by the Guardians on the tombworld of Ysmault.
After the wars, all the stray mystical energies in the universe were gathered and bound in an orb called the Starheart. This collective force was hidden in the heart of a star and grew in power and eventually gained self-awareness as the Green Flame of Life. Though the Guardians were powerful, the force of magic was something that could not be contained forever. In preparation for this day, the Starheart willed a small portion of itself to travel through the universe to fulfill its destiny. As it traveled through space, the piece of the Starheart gathered debris over the centuries until it resembled a meteor.
Two thousand years ago, the Starheart fragment found its way to Earth and, after fusing with the evil spirit of Yalan Gur, crashed as a meteor in China. A man named Chang eventually shaped the meteor into a lantern. Centuries later an insane lampmaker named Billings reshaped it into a train lantern. In 1940, this lamp was found by Alan Scott who used its incredible incomprehensible power to become the first Green Lantern on Earth in centuries.
Decades later, an alien named Zalaz stole the Starheart to raise his beloved M'la from the dead. Opposed by Alan Scott, Hal Jordan and Green Arrow, Zalaz retreated into the Starheart and awakened M'la inside it. M'la became the Starheart's guardian. The original consciousness of the Starheart later reawakened and destroyed M'la. It grew in power and sought to control Alan Scott's life, making him a young man again. Scott and the mystic Green Lantern Torquemada managed to contain some of the Starheart's evil energy, but the Starheart itself escaped.
After the events known as Zero Hour the ring and lantern were depowered and the Green Flame dwelt within Scott's body. More recently, the Starheart resurfaced in another realm from which it took control over Scott's son, Obsidian, in an effort to steal back the power from Alan. By sacrificing her own Starheart powers, Alan's daughter Jade defeated the entity. The Green Flame now makes up Alan Scott's entire body, and he uses the power to battle evil as Sentinel. Wood is its only weakness.
Holy anachronisms, Batman!
This article is in need of updated information.
Starheart Mysticism: the mystical power and ability of the Starheart, an ancient artifact created by the Guardians of the Universe. The Starheart is capable of many magical and mystical powers and abilities that include but aren't limited to the following:
- Phasing: The ring permits to its wielder to walk through obstacles as if was a ghost. 
- Metal Manipulation: The wielder will gain mastery about all metals and be immune to it.
- Eternal Youth: The artifacts mystical properties also imbue one with seemingly vastly extended lifespan; decelerating the aging process.
- Flight: allows one to fly at varying incredible speeds through the air.
- Energy Constructs: and create solid objects such as giant hands, walls, shields, force fields, battering rams, cages, slides, safety nets, ropes, chains, platforms, hammers, and grappling hooks.
- Protective Force Fields: He seemed to have a relatively permanent personal force-field that protected him from bullets and the like (described as an “invulnerability to metal”).
- Matter/Energy Manipulation: The star-heart is capable of transmuting and changing energy and matter. The star-heart can also manipulate energy for more subtle effects like bending light to make the user invisible.
- Energy Projection: The Starheart can project different forms of energy that are both mystical and non-mystical.(electricity, magnetism, etc.)
- Reality Alteration: The Starheart can affect and change reality to a limited degree.
- Teleportation: allows its wielder to magically teleport across short or long distances in a flash of dazzling bright green light.
- Hypnosis: The ring can hypnotize persons, and the Starheart itself could hypnotize the wielder to fulfill its own agenda.
- Time Travel: Once, the Starheart opened a time-portal by 24 hours. The ring needed the combined willpower of Alan Scott and all the Infinity Inc. members to return the later ones to their own time. 
- Power Limitation: The ring is ineffective against wood and plants.
- The ring must be recharged in the Starheart every 24-hours to keep his potency.
- The abilities of the ring are powered by the willpower of its wielder.
- The Starheart is referred by this name by the first time in Green Lantern Vol 2 111 (Until then only the meteor and his force, Green Flame of Life, were known). The Green Flame of Life admits be part of the Starheart in Green Lantern Vol 2 112.
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