Background
The Crystal of Being, 2 BBY
The Crystal of Being is a crystal found in Beasts, Jod, and Red Rock Kingdom myths dating back as early as 27,100 BBY for the Red Rock Kingdom and even earlier for the Beasts. It is thought that the mythical crystal was the being of the Capital World of Prime, its fully sentient-being controlling the millions more semi-sentient Red Rock.
Whether the crystal was the actual consciousnesses of the world itself, however, is up to debate. Most scholars believe that The Crystal of Being was in fact part of a long forgotten alien empire and that the crystal crash landed on the Capital World of Prime and started multiplying itself deep within the inner workings of the world over hundreds of years, soon growing through the planet's surface to show the telltale signs of Red Rock.
If The Crystal of Being is---in fact---real, it could point to a long dead alien civilization and its purposes for Red Rock, which a handful of scientists think the Red Rock formed their starships, vehicles, weapons, and even their physical form. The crystals, meanwhile, were miniature self-contained armored pods that contained the alien race's most vital functions, essentially allowing the beings to reproduce various physical forms of Red Rock, as long as their "central crystals" were not damaged.
As to why & how this particular being grew through a planet, no scientist knows for certain, although some feel it is because the being itself is damaged beyond repairing itself fully and is slowly dying over thousands of years. The planet allows the alien being to repair itself minimally and remain alive longer, the planet acting as a natural cocoon with healing properties and a medium for which to grow itself (hinting that the Red Rock and central crystals themselves need certain demands met in order to grow and live properly). This growth allows the being to essentially reproduce itself and strengthen itself through size, giving to the thought that the larger the alien is, the healthier it is through process of having more areas to move itself from dying areas to living areas within its size.
With the destruction of the Red Rock Kingdom & their home planet, The Crystal of Being has become even more mythical if it still---or ever did---exist. Sought after for more then its mythical value, The Crystal of Being is said to be able to recall all pieces of itself (the Red Rock) and once again become whole as a planet, issuing in unlimited power through its properties. The Galactic Empire is utilizing this approach through Project Zero.