From Marked wiki
The main setting of Marked revolves around a small part of north-western Massachusetts in the United States. There you will find the town of Whitley and its recently created Supernatural Quarter as the growing center of the world's supernatural community. The Supernatural Quarter holds the Sanctum Institute, an organization devoted to the support and education of the supernatural community.
Of course, the world of the Marked is not limited to just that corner of Massachusetts. There is a vast history and many cultures that exist out in the world beyond -- even crossing entire dimensions at times.
The Marked, Half-Breeds, Daemos and their sometimes fantastical cultures and locations are all very much a secret from the regular world that we are all quite familiar with. Human governments have no knowledge of any of this and many who might have seen something of the sort are considered insane when they go and try and tell their friends and family.
Secrecy, however, is very carefully maintained by the Hidden World. Arbiters maintain the balance of the world and as such, are quite brutal and efficient when it comes to ensuring that secrecy. Most Half-Breeds know of Arbiters only through oral histories and legends, and many doubt their existence. Few who see an Arbiter live to tell the tale and those who threaten the secrecy of the hidden world are swiftly eliminated. Throughout history, the Arbiters have "pruned" races or cultures if they see that they are growing too large to retain secrecy.
Dimensions live completely separated from each other. Impenetrable walls are raised between the dimensions and each holds their entirely own universe with its own way of life. With only one exception, the dimension is totally cut off from all others. Travel between them is impossible. The Daemos Realm has found itself the power to cut through dimensions. They have used that ability to destroy everything around them. The Human Realm is simply next on their long list of conquests.
The Human Realm
The Human Realm is where our entire universe exists. Since before the beginning of time, the Human Realm had been in no danger from other dimensions. However, the interdimensional wall that was supposed to be inpenetrable was cracked around 3300BC. Thousands of years later, those cracks grew into gaping holes, leading to the onslaught of the Daemos and the resulting rise of the Marked. It is said that the Daemos were finally forced back around the 7th century and many of the Marked gathered together to rebuild that interdimensional wall. Some cracks, however, remain and the Daemos is a forgotten threat.
The Daemos Realm
The Daemos Realm is not a part of the same universe that Humankind live in. It is another world entirely, but one that still carries its own long history, traditions, and cultures. The creatures who inhabit this world are all of the Daemos race, and while their individual subraces are seemingly limitless, they all share one thing in common; a want for destruction and chaos. The environments of the realm are just as diverse of that in the Human Realm, though far more alien and often darker. A bloody history has been etched right into the land that has only ever been touched by Daemos-kind.
There was a time when passage between the Daemos Realm and the Human Realm had been an easy one, though only for the Daemos themselves. The barrier between the worlds had once been thin, full of holes, and it was a simple matter for Daemos to slip from one world to the other. Marked and Half-Breeds, however, were not capable of such a feat without help. It was either the Daemos themselves who could bring them over or one who had the ability to jump through space itself. For example, a teleporter could have moved from one world to the other, though they would have found existence in the Daemos realm difficult to bare; the gravity is far harsher and the air difficult to breathe.
Planes of Reality
There are many different planes of reality that exist in any and every dimension. These are different "layers" of reality, stacked one on top of the other. While some have been discovered by both mundane humans and the far more special inhabitants of the world, there are still many more waiting to be found. They are outside of the physical realm and each tends to serve its own purpose. Some are accessible to mortals, but some are inaccessible by normal means. Each plane outside of the physical one holds only one rule; Lifeforms never originate from a Plane. Most planes cannot sustain mortal life for long periods of time, though there are occasionally exceptions, often on a race-specific level, to that rule.
The Mortal Plane
The mortal plane is the one that everyone is intimately familiar with. Humans, Marked, Half-Breeds, and Daemos alike all travel and live upon this plane. It is designed to support the life of mortals. Occasionally, other planes may cross over, such as when a ghost is supposedly spotted. While this is not a common occurence, it is completely natural and does not upset the balance of the world.
The Shadow World
The Shadow World is a barren, desolate place that is accessible by those who can travel via shadows. Within the Shadow world, they effectively open up doors of light that will lead them back to a location on the Mortal Plane.
The Spirit World
Spirits of the dead who have not yet traveled on to whatever the afterlife consists of wander the Spirit World. Some are thought to have unfinished business, while others may simply be trapped for reasons unknown. ;If one were to visit the Spirit World (which is only possible by detaching your spirit from your body and then finding a way into it) they would only see a world of fog overlaying the physical one. Half-Breeds, Daemos, and Humans (and those who were Marked before they died) all wander here. Due to the fact that these spirits were once mortal, the spirit world is considered "closest" to the Mortal Plane. This causes the occasional ghost stories that pop up from time to time, as the intersect almost causes a "window" to open up into the Spirit World. When such a window opens, it allows a mortal to see through to the Spirit World or for the spirit to reach through and effect the mortal plane.
The rules of spirits, however, has changed since the Ghost Apocalypse. Before, they were completely unaware of their surroundings and trapped in a silent, faceless suffering. Any spiritual activity was attributed to undirected and unfocused pure emotions that filtered through a window from the Spirit Realm.
After the apocalypse, spirits became more aware of their surroundings, but to a limited degree. They will be detached or they will be focused on or trapped within specific emotions, memories, or thoughts. But when they cross over to the mortal realm with more than just their spiritual power, they will now be able to directly react to happenings around them.
The number of spirits in the spirit world has sharply decreased since the River of Souls event. Spirits are no longer becoming wrongly trapped here and can move on more easily. Those that linger usually have attachments or something else (sometimes supernatural) holding them in the spirit plane.
The dreamworld is for sleepers all over the world. It is an ever-changing place that is split among the dreamers. Every dream has its own corner, and while crossing between dreams is not very common among regular individuals (with the exception of lucid dreamers), there are those who have special abilities that are focused within the Dreamworld.
The Emptiness is simply nothing at all. It is the space that exists between the different realms and dimensions. Those who have slipped between the cracks of the world may have found themselves trapped here in a limbo that provides them with no air to breathe. They usually do not last long. Teleporters with especially unstable powers find themselves most susceptible to slipping within the Emptiness. However, the cracks are so tiny that it usually requires and extra push against their powers to find themselves trapped within.
The Separation of Worlds
Towards the end of The Great War between the Marked and the Daemos, a segment of the Marked were able to construct a barrier between the two worlds. This was what had effectively ended the war, cutting off the Daemos' access to the human world. However, there are still occasional rips in the barrier that one of the lesser Daemos can slip through. The smaller the rip, the weaker the Daemos must be who is passing through. These rips are an incredibly rare occurance and usually only stay open long enough for a Daemos or two to slip through. However, there is another method that can be employed and this is through established portals. At the present time, the only known way to establish a portal is to gain an artifact of Daemos origin that was designed to cut through the barrier. One such artifact had once been part of an ancient Daemos Artifact, a sword that could cut through anything. This sword was seized by the Marked and after spending years attempting to destroy the object and its power, all they could find to do was to break it apart
The power of that sword is now fragmented into three artifacts of unknown identity. The artifacts can be used to open a portal between the worlds that a Daemos could slip through. These portals only have a number of "uses" before they simply vanish, but it is enough to take two or three trips through the portal. And while a Daemos can simply pass through the portal, the Marked and Half-Breeds are unable to do so without some method of teleportation or spatial travel.