The Possible

There are entities not born of flesh and bone, but of meaning. Beings that originate as abstract notions adrift in the vast ocean of unrealized possibility within the Tapestrum Arcanum.
  These beings are called the Possible, and they exist beyond the veil of reality, in a state best likened to a yearning for existence.
 

To Be Realized

The Possible are not ghosts, not gods, nor hallucinations, though they may appear as such to the untrained eye. They are ideas, concepts with desire, each one yearning for realization. Their only way into the material world is through manifestation, which they cannot achieve on their own. For this they need hosts, minds shrewd enough to accept them and compulsive enough to make them real.   These ideas often begin as flickers; a recurring image, a fragment of melody, a strange name whispered in dreams. The more the host dwells on it, sketches it, writes it, sings it or even just thinks about it, the stronger the Possible becomes. Once complete, once the idea has been realized, the entity crosses over.
 

To Be Forgotten

For a Possible to become real, something else must become unreal in exchange. That something is most often the host, the one who nourished the idea, shaped it and gave it form. Once the Possible is almost fully realized in the world, the host begins to unravel.
  They don’t die in the traditional sense. They begin to disappear, piece by piece. People forget their face and their name, as do they themselves. Any written records about them vanish, ink simply evaporating from parchment. Portraits and paintings of them lose their faces before they vanish from them entirely.
  Spoken memories involving them become confused, then are forgotten. They become an idea in the Tapestrum, floating, fragmented. And in that formless, conceptual state, perhaps they too begin to yearn for realization.
  It is important to acknowledge that the Possible are not evil, per se. It is the nature of ideas to want to be. Perhaps the Possible are a natural phenomenon and all things get their season in the sun until they are forgotten again and make way for new ideas to emerge.  

Known Possibles

It is highly likely that "A Picture of Me", the anomalous painting that proved to be the mysterious end of the Glarithian painter Larion Voskar was a Possible seeking entry into Nascindor. It is unclear whether or not whatever it is actually made it through or if it is still clawing at the boundary between reality and the conceptual, only just unable to break through.
  Another suspected Possible is the Entity that is bound to the vase that is in the possession of the Enlightened Few in Pluthem. The Entity's proclivity to entice those who interact with it to touch it so it can presumably absorb their potential certainly fits the bill for a creature that craves for actualization.
  Finally, some have put forth the rather disconcerting idea that the strangeness of the Varlem Desert is an exceptionally powerful Possible trying to make its way through. But if that is the case, where and what is the host that is realizing it? And what will be traded off if it manages to become real?