Foldspaces

Foldspaces are a general term for pocket dimensions of several subtypes, which are recognized by the System as such. They are a crucial element of the Divinity Framework, but there are also used by other entities of sufficient level of power.   They are also perhaps the only remaining way of travel between the universes, although with the fall of the Dominion of Mankind this has began progressively rarer, as less and less powers out there are capable of such a feat.

Foldspaces on the most basic way are 'places bigger on the inside than on the outside', requiring a significant degree of warping reality to properly establish. However, not all places like that are considered Foldspaces by the System, as that requires certain degree of stability.   They are created by a multiple ways. Demigods are capable of doing that naturally, exchanging their gathered divine power into creation and establishment of those through the Divinity Framework. Powerful organization of mages might pool their resources into forming one, which is a potent way of showing your might - pool enough of efforts into it, and the System will recognize it as a Foldspace.   In the past, they were created by the Dominion of Mankind through purely technomagical ways. That was used during the Great Multiversal War for both combat and multiversal transportation. This, in turn, was a manmade copy of foldspace-equivalent used by the Dark Lords to invade Earth.   The sufficiently large servitor groups are still capable of forming their equivalent of foldspaces, although they aren't recognized as such by the System due to the System being actively hostile to the servitors.

Foldspaces that are recognized by the System can be easily modified. Divinity Framework will expand to include a new page, allowing the demigod to modify their surroundings by spending their divine power. This includes several things.   1. Reshaping the area itself, adding new corridors and rooms and reshaping those already present there. Smaller foldspace typically stay as a single level, just much larger than it should be. Larger often take up a layered form, with demigod's lair located at the lowest level of the foldspace.
2. Furnishing and establishing Zones. Foldspaces managers aren't able to create whatever they want. However, the Foldspace is capable of expanding its conceptual contents. In shorter words - get yourself a wooden chair, bring it to the Foldspace, and you'll be able to replicate it at the appropriate cost in DIvine Power.   Zones, in the meantime, are a different themes of the area. For example, bringing enough of mine-themed objects to a cave-based foldspace will allow the manager of it to reshape the aesthetic of a part of it (often a whole layer to keep it simpler) to resemble a mine, all while sorting out the appropriate mine-themed decor pieces into a separate submenu for easier navigation. This will also alter the corridors and walls on its own.
3. Introducing spirits to the area. Foldspaces, due to their very nature, have a naturally denser background mana presence, meaning that spirits find it a pleasant place to be. The Foldspace's managing system allows to anchor their existence to it.   This means that slain spirits will find their existence 'restarted' by borrowing the power of the Foldspace to reconstruct their existence. It won't be immediate, tough. This deal also means that the spirits will find themselves compliant towards the will of the person now governing their existence.
4. Introducing summoned entities to the area. Foldspaces in the Vassal Worlds have a background magic level more akin to what the Throne Worlds. This means that it's significantly easier on their nature.   It is entirely possible to summon entities from a Throne World and have them bound to the foldspace. They are sapient and, in fact, often belong to the same species as the owner of the foldspace. They descend to the foldspace in a form made from the foldspace's mana, something fundamentally impossible outside of it where they can at best appears as magical projections.   This means that they exist there physically, although they cannot leave the foldspace for long.   Such 'hirelings' are a notable buff to security. They cannot fully die, as their soul was never there. Their reason to agree to this deal varies. For some it's entertainment and wanting to see the other worlds a little. To others, they want to fight and train their skills. Some come because they wish to defend a realm of a demigod that they agree with on political and moral grounds.

There are secular foldspaces, as mentioned briefly above. They are created by particularly powerful non-demigod individuals, groups of those, powerful artifacts lost somewhere in the unknown beyond and so on. When that happens, the resulting foldspace won't be governed through the Divinity Framework.   Instead, there'll be something akin to a physical terminal formed somewhere within it (it also can be moved). It forms open to everyone, but one can limits the ability to use to certain people by forming physical keys that need to be kept on a person, or by introducing a password lock.

Foldspaces can technically be used for multiversal travel. There are bubbles of space that - when they are big enough - are only tangentially connected to their original world. What you need to do to achieve travel is to fully disconnect from one world and connected to another.   This is easier said than done. It's easy to fail to reconnect to another world, and instead trap yourself in a small bubble of existence. You can accidentally reconnect to a deadly place and, for example, have your domain flooded with magma when you open the entrance.   In general, navigation is extremely hard, and only somewhat aided by the System. Computers capable of calculating such movement properly are only available in the Throne World of Ferra. The alternative is attempting to navigate through links in the Astral Network but this, too, is dangerous without a divine aid.   This means that when it does happen, it's often done by collapsing culture whose gods aid the evacuation of what was left of their faithful to a greener pasture. With numbers of people involved rarely surpassing ten thousand. And even that requires extremely large foldspace.