World Shards
A World Shard is a fragment of a World Heart. Some of them are tiny, like the Cloisters of Spira. While others are massive, like the Giza Plains. Generally, for a Shard to have survived the fall of a world to Darkness, it would have to have had meaning to people. It has to have been remembered in their own Hearts, and matter to them.
Properties
As a piece of a World, a World Shard has unusual properties. Often a Shard will have a resonance of some kind, relating to what it used to be a part of. For example, a Shard of the Agrabah Bazaar may relate to heat, trade, loss, or other facets related to said world. Those who have the needed knowledge can attempt to leverage these resonances in various forms, including advanced Sorcery, manipulation of the Dream, or crafting a device that can make use of those abilities via Technology.
Shard Creation
Making World Shards are both simple and terrible at the same time. All one has to do is force a world to break apart and be consumed by the Darkness, either slowly in the form of the Dark Seas, or all at once, by guiding the Heartless towards the World’s Heart, immediately devouring it.
Those people who do not escape the Darkness lie suspended within the Shard, either sleeping until such time as the world is freed… or perhaps becoming Heartless themselves if they are truly unfortunate.
Locating A Shard
World Shards will then begin to appear, often in the same manner as Gummi Blocks, falling from the Darkness into other worlds. Oftentimes a World Shard will land near something that shares a resonance with it. a Shard of Agrabah might land in a desert or be picked up by a genie... or an evil sorcerer, for example. Other times, it might seem completely random.
The presence of a Shard can be discovered. As a fragment of a Heart, it can be located through any method that would sense such things. Heartless naturally seek out World Shards to return them to the Darkness, while Sorcery and Technology can be used in various ways to attempt to do the same. Using something related to the Shard can help immensely… But often, locating a Shard is only half the battle. The Heart is a source of power in the worlds, a fragment of a World Heart being just as valid as anything else. Often, things seeking this power will have acquired them… And they will not let them go easily.
Restoration
A World Shard can be restored to existence through several means. The simplest is to use a Keyblade, as the Keyblade is a channel towards interacting with the Heart and all it contains. Other methods may be available for those who are willing to find out what the Shard will respond to. Some might require a song. Others, great sacrifice or bravery. What a Shard requires always is related to the world it has come from. If one is not careful, however, they can have destructive consequences on the world around them… or the contents of the Shard itself. One cannot take such efforts lightly.
There are rare situations where a World Shard will land in such a manner that it will immediately begin restoring itself. Such locations may have extremely powerful bonds with the people of their world, or the Shard may have landed within a place that resonates extremely strongly with it… Or other, more mysterious forces may be at work. While this /may/ be beneficial to those who reside within the Shard, the process can be devastating for the environment around them, or warp the environment in strange ways, as the process is completely uncontrolled. Buildings may appear within buildings, or castles being laid beneath the ground, for example.
If enough World Shards of a single World are gathered together, one might be able to restore them… but this often requires the assistance of someone who was profoundly linked to the world. This connection is usually the hallmark of a Dusk Princess. This connection to the world is a channel through which the Heart can be reforged, and is a dangerous process. Powerful Heartless will inevitably be attracted to the World Heart in an attempt to consume it again. The effort to reforge the Heart is also extremely exhausting to whoever it is that serves as the connection, and the state of the Heart when completed will often reflect the nature of the person who restored it.
Even after all that, the Heart is restored... And unlocked. A Keyblade Wielder is needed in order to truly secure the world against Heartless attack, by locking the World Heart and sealing it against casual invasions.
