The Sun Crystal (also known as the Solar Crystal or Power Crystal) are a special kind of crystal that fell to Earth from outer space. Charged with cosmic energy, their power was first used by the Y'Lyntians. After the fall of their empire, the remaining crystals came into the custody of various factions, such as the Turtles and the Foot.
Sun crystals are typically blue with larger more powerful ones being brighter blue-white. They store cosmic energy and are periodically recharged by the alignment of all the planets. They can store cosmic energy for centuries or even millennia according to the size of the crystal. Smaller crystals (such as fist size) are usually unable to store the energy for a particularly long time, especially when used much, but within the radiation field of a larger crystal memory, they can be used as long as the larger crystal memory is not depleted.
The crystals are susceptible to thought waves; they can either provide visions to a dreamer who is in their immediate vicinity or, with appropriate practice, provide their user with the energy they contain. Thus, various supernatural effects can be obtained, which, among other things Y'Lyntians exploited to mutate human slaves to new environmental entities, used them as a weapon similar to a laser beam, create beings of pure magma, or raise Y'Lyntius to the surface of the Earth.
The crystals themselves are largely immune to most influences that could damage other materials such as heat, drilling, or blunt force trauma; fragments of this crystal have survived even a prolonged stay in liquid lava intact. The only known method of dissolving the solid form of the crystals is by irradiation with an ultrasonic frequency which relaxes the molecular bonds of the crystals and liquefies them.
The exact origin of the crystals is unknown, but they fell to Earth from outer space as a meteor shower over ten thousand years ago. They do not appear naturally on Earth and the remains of this shower are the only known source of this type of crystal. The meteor shower landed on the island of Y'Lyntius, with the largest fragment landing on the tallest mountain - it was called the Sun Crystal. The inhabitants quickly learned to use the crystals and made a tremendous technical and cultural step forward. However they advanced so much so fast they began to think themselves superior to other beings, leading to tyranny. They captured humans from various cultures and turned them into slaves that maintained the extravagant lifestyle the Y'Lyntians came to enjoy. If the human slave was unable to preform the duty they needed, they were mutated by the Crystal Sun into a more suitable form. Eventually, the human cultures banded together in a revolt and the Y'Lyntians used the energy of the Sun Crystal as an energy beam weapon against the attackers, but their slaves rebelled. The energy beam was turned back onto the Sun Crystal, causing a catastrophic chain reaction that caused the island to sink into the sea.
The Y'Lyntians managed to salvage some of the sun crystals they used to power an underground city called New Y'Lyntius. The largest piece was hung from the ceiling of the cavern and called the Crystal Moon. Pieces of the crystal were also recovered by the Avians, who would use it to power the floating cage they were once forced to live in, making it their home. The Y'Lyntians created an observation post under what would be New York to observe humanity, which was also powered by sun crystals. However, the energy began to dry up so the Y'Lyntians, under the Archmage's supervision, went into a deep sleep that would last until they were re-energized by a new alignment. The Foot found at least one piece of crystal they used to power an underground genetics lab. The Turtles would go on to find several pieces of crystal in their new hideout, unaware it was the old Y'Lyntian observation post.
When the Y'Lyntians attempted to bring their old sunken homeland back to the surface after their resurrection (despite the geological disasters that would haunt the earth during this process), the Turtles and the moderate Y'Lyntian Versallia prevented this by causing a fatal energy feedback. New Y'Lyntius was completely destroyed in this catastrophe and sank into the lava lake around the colony. The Crystal Moon also fell into the lava. As the sun crystals are unaffected by heat and the Crystal Moon has fallen into molten lava before without harm, it is likely still whole.