The Shadow Crown, nicknamed the Moon Hat, was the realization of many years of research into dark side and Sith lore by Cronal. This crystalline "hat" would be worn by a mortal being whom Cronal could choose to inhabit to extend his existence, rather than Darth Sidious' technique of using a clone body to cheat death. Using his Shadow Crown, Cronal submitted his devotion to the Way of the Dark. Cronal would connect directly to the Shadow Crown with his own version, called the Sunset Crown.
When worn, the crown would project a holographic representation of Cronal over the face of the wearer, activated by several hundred pointed crystals that projected into the skull of the wearer. Once activated, the crown would concentrate the Dark Side of the Force on the individual, allowing Cronal to control them. Luke Skywalker noted that it was a heavy object, at over two kilograms.
The crown, however, proved to be very dangerous to its controller, especially regarding its meltmassif-controlling properties should the connection be interrupted. This is ultimately how Cronal was killed, when Luke Skywalker managed to stop his control over the crown, causing Cronal to be covered in meltmassif via his own orafices, petrifying him and his ship in Hyperspace, resulting in their disintegration.
Cronal traveled into the far reaches of the Unknown Regions via his Darksight vision, and visited such sites as the Gunninga Gap, Valtaullu Rift, and the Temple of Korman Lao. There, he discovered information and knowledge that led him to the tomb of Dathka Graush in the Valley of Golg on Korriban. The knowledge he acquired at the Temple allowed Cronal to access the spirit of Graush and learn of Sith alchemy that could create a device which would control a living crystal, Mindorese meltmassif. Cronal would form a larger structure of this substance, and in 5 ABY, Cronal chose Nick Rostu to wear the Shadow Crown and be his chief Pawn, "Shadowspawn." However, he soon decided that in order to restore the Empire under a new leader, he would need a far greater being to wear the crown, namely Luke Skywalker.
Cronal was not the only Rhandite to hold such knowledge, as Blessed Toxmalb also possessed a Shadow Crown buried under his skin.