The Heart of Atlantis
The Heart of Atlantis is one of the most powerful of the World Keyholes found across the universe, having been forged from an alien comet made by the Celestial Alpha Beings and a sizable portion of the true light originating from Kingdom Hearts itself. Many of the Keys to Power forged by the High Council received their power from the Heart of Atlantis, which was the true heart of that world, even after the empire itself was split across various worlds during the fall of the Lands of Legend. Even the Silver Imperium Crystal, the very crown jewel in Zeus' private collection, originated as part of the Heart of Atlantis' crystal core.
It is generally shown as a glowing teal/turquoise-colored, rotating, translucent crystal orb with a jagged surface emitting a flaring white aura, and is seen levitating with stone effigies of the past kings orbiting around it. Its immensely incomprehensible abilities provide the Atlanteans with extended longevity (capable of living for hundreds or thousands of years), semi-immortality, youth and beauty, and technological advancements.