Install and upgrade a game system

A system supplies a world's character types, sheets, rules, and game data. Aether locks each world to an exact system version and the packages it needs, so a campaign cannot change underneath the people playing it.

An empty world may choose an installable system. A world already using that system may install an update when the creator provides a supported path from the current version. An established world cannot switch to an unrelated game system; create another world for that game.

#Create a world from a listing

1. Open a system in the Marketplace and choose Create world with this system.
2. Review the creator, verification state, and version.
3. Review what the system adds: character and item types, sheets, companion tools, automated rules, starter content, and requested permissions.
4. Read the license and creator rights declaration. The declaration is supplied by the creator; it is not an Aether copyright verification.
5. Review its required and optional packages, choose whether to include starter content, name the world, and confirm.

Aether checks every required package before creating the world. It verifies all package files and activates the system only after the complete installation passes validation. If installation fails, Aether removes the incomplete world instead of opening it with a different or empty system.

#Understand required packages

Open World settings → Installed mods. A package labeled Required by system is locked to the system. It cannot be disabled or uninstalled on its own. Open Game system to change the complete set through a compatible system update.

An optional package may be absent only when the system declares how it behaves without it. A missing or incompatible required package or integration prevents the system from starting.

#Review an update

Open World settings → Game system. The installed row shows the system, version, package identity, and current state. When a compatible update is available:

1. Choose the version and select Review update.
2. Read its changelog and verify the package identity.
3. Review added, removed, or changed packages and integrations.
4. Review permission changes and every data-upgrade step.
5. Confirm the review, then choose Stop world and upgrade.

Aether stops the world before changing its data. It creates a recovery point, prepares the new packages, runs the system's upgrade steps, validates every changed document, and restarts the world only after the complete update succeeds.

#Failed upgrades

If an upgrade step or final validation fails, Aether discards the attempted update and restores the previous recovery point and installed packages. The settings notice names the failure and confirms whether recovery completed. The previous version remains the active campaign version.

Fix or replace the target package before retrying. The initial check confirms that an upgrade path exists, but that path still has to process the world's actual documents and may fail.

#Manual downgrade

A lower version appears only when the installed system provides and validates a path back to that version. Selecting it is a manual downgrade with the same recovery point, maintenance, data changes, and validation sequence. There is no arbitrary downgrade or automatic conversion to an unrelated system.

#Missing or tampered packages

At each startup, Aether verifies the exact installed system and its required packages. Missing, changed, or incompatible package files leave the world data in place and report a failed system state. Aether does not silently load a demo, an empty system, or a nearby version.

Restore the exact package id, version, and hash named by the failure. Then open World settings → Game system and choose Retry exact package. If the exact bytes are no longer available, keep the world stopped and contact the package creator or Aether operator before changing any world files.

#Empty worlds and existing campaigns

An empty world has no active system and no system-owned documents or history. System selection is refused as soon as a world contains an active system or system data. This prevents established campaign records from being treated as another game's data.