Realms, by and large, are separate from one another. They have boundaries and separation, usually expanses of unclaimed cosmos.
As a norm, Realms are not adjacent enough to freely move from one real to another. However, that doesn’t mean that Realms cannot interact or trade with one another.
Doors
The Eschatos Diagram is a map, among other things. If you know the location of a Realm, you can open a Door to it. It costs Providence (Fortune, Luck, etc.) to do so.
Doors can be guarded, though it fixes the Guardian to the Door. More than one Guardian can be assigned.
A Paradigm automatically guards Doors in their Realm (unless they choose not to) as long as they are present in the Realm.
One-Way Door
The least expensive and simplest Door to open. One-way Doors open for a short time and then immediately close after someone or something passes through. Most commonly used to send goods or people to another Realm.
Two-Way Door
A Door built to allow travel from both Realms. Like a One-way Door, these are short lived and close after travel occurs.
Door and Bridge
A Two-Way Door where a Bridge made out of Fortune is crafted to allow long-term entry and exit. A Door and Bridge is maintained by taking a small amount of Fortune from the Realms connected. The Bridge exists as a small, pseudo-realm similar to a Paradigm’s Seat, except it is lawless, e.g., the rules of the connected Realms do not apply on the Bridge.
Door and Contract
A form of Door and Bridge bound to one or more conditions established when the Door and Contract is created. Examples: Door that opens on a cycle, based on certain events or times, when a specific item is used, a particular bloodline, etc. Conditions are as varied as they get.
Pinhole Door
Initially created as a Fortune saving mechanism. A special One-way Door that requires a tiny amount of Fortune to maintain a connection. Either end can provide the Fortune. The owner of a Pinhole Door can upgrade it to another type of Door at any time by applying Fortune. You cannot assign a Guardian to a Pinhole Door.
Parasite Door
Early Realms learned to weaponize the exchange, e.g., Doors, in the Eschatos Diagram. Parasite Doors are used to attack, creating a special kind of Two-way Door that is wide open on one end and small on the other. Latching on like a lamprey, these Doors drain Fortune from the attacked world. Aside from a few special beings and materials, they cannot be used for travel.
Door States
Doors are either Open or Closed. An Open Door is visible to anyone who bears the Eschatos Diagram. You can approach an Open Door and determine where it leads and look through it to observe the other side. A Guardian, of course, may prevent anything more than detection, if they will.
A Closed Door is visible, unless otherwise protected. You cannot see where a Closed Door leads, or whether it has a Guardian without opening it. A Closed Door must be opened to Contest it. A Guardian can choose to force you to Contest a Door to open it.
Contest a Door
A Guardian can stop someone from using a Door, including a Realm. When that happens, a Door is Contested, causing the two forces to battle.
The Guardian can either resist with Fortune directly or fight the battle on the Bridge. A contest of Fortune is exactly like it sounds and whoever expends the most Fortune wins control of the Door.
When the battlefield is the Bridge, both forces bring their forces to Bridge attached to the Door. It costs Fortune to move troops to the Bridge, though any forces involved in the initial Contest are considered free (for both sides). A battle continues on the Bridge until no more forces exist or one side gives up.
A Bridge Battle is, in effect, identical in many ways to a Realm War. That means the players involved can expend Fortune, call Allies, and use Powers at their disposal during the battle.
At the end of a contest, the winner decides what to do with the door. They can take control of the Door, becoming the Guardian. The winner can destroy the Door, removing it completely. Or, the winner can use/not use the Door, not changing ownership.
As a note, a pecking order exists that can disrupt the entire Contest process. Any authority one step higher can define the choice of Fortune/Bridge for a Contested Door. Any authority of two steps higher can eliminate the need for a contest completely.
The list, in order of precedence, is: Primal Realm, Free Realm, Sleeping Realm, Paradigm, and Guardian. Immortals interact as the Realm equivalent.