Void

Void is an inky-black substance that is only known to exist in the Abyss. It plays a major role throughout the history of the Kingdom of Hallownest, and is the answer to many of the inhabitants of the ancient lore before the creation of the kingdom.

History
The power of the Void was discovered and used by the Pale King for his constructs and creations. Located in the Abyss, a stark land devoid of life, it is unknown how Void is created, although the King used it to its fullest. His first creations appeared to be the Void Tendrils, as they were molded in the Abyss rather than his Palace. This is possibly even before the Palace was created. He gathered Void using large cauldrons and brought it up to his workshop in the White Palace, where he would construct molds to put Void into. Labeling it with a seal, such as for the Kingsmoulds, "...SERVE...", the King would create constructs that would be put in shining white armor (this included the Wingmoulds.) Then, the King began to construct beings of Void that were known as Vessels. He would use these Vessels to contain the plague that was quickly spreading over his kingdom. He created thousands and thousands of Vessels, each of them dubbed a "failure", and their husks cast off into the Abyss. Soon enough, the floor was completely comprised of the broken shells of the Vessels that were cast off. That left the beings of Void to roam around the Abyss with no containment to flourish in. Large towers were constructed in the Abyss, used to ward off the Void (they appear to be large lighthouses, and the light would repel the darkness.) Finally, a Vessel was found to house the infection, and the entrance to the Abyss was sealed with the brand of the King, so that no one other than the King himself could enter. "We shall enter that place no longer."

Constructs

 * Void Tendrils - Possibly the King's first experiments with Void. The desired shape was first outlined and then filled with Void.
 * Kingsmoulds - Constructed along with the Wingmoulds in the King's workshop. The desired shape was outlined a egg-shaped case, and labelled with the seal "...SERVE..."
 * Wingmoulds - Constructed along with the Kingsmoulds in the King's workshop. Unknown how the shape was created, although the armor was hung from the ceiling.
 * Siblings - The Vessels that would house the plague, including the Hollow Knight. Thousands upon thousands of these were created, only one proving to be the pure Vessel that would contain such an infection.
 * Hornet - Hornet herself mentions that she is similar to the player and the Hollow Knight, created by the Pale King as a gift to Herrah the Beast.