Halci was once a much simpler realm: no spirit side, no god-places, no ever-threatening Void and Dark. Just the daylight side and the Shadow Realm.
After the Descent of the Wraiths, and during the ensuing Wraith Wars, the situation was changed by force. The Ravager, fearing that the wraiths would kill all the spirits, endeavored to tear the spirit side away from the physical — and succeeded with the help of the raptor spirits. The Spirit Realm was displaced just slightly, but it created enough of a barrier for the wraiths to be unable to perceive or reach the spirits, even while the spirits retained contact with their mortal children.
However, even the slight displacement caused rifts within the newly created Spirit Realm. The greatest of these was the gap that formed in the narrow space between the Physical Realm’s surface and the Spirit Realm’s surface — the Grey, a thin space through which any lost soul could slip, whether mortal or wraith, if no other connection tethered it. Formless and chaotic, the Grey is unmapped and unmappable; traversing it successfully requires a tether to the Spirit Realm or a wraith spire, else one could end up wandering forever.
Beside the Grey, other shards were shaken free of the main mass of the Spirit Realm. Some were claimed by individual spirits, to serve as their private homes and the destinations for their followers in the afterlife. Later, after the Awakening of the Gods, the Awakened deities themselves claimed many a shard. Unlike the main Spirit Realm, these shards are not tied to a physical location; they can move at will, and can also settle themselves flush against the Physical Realm if their owner has the desire — and concentration — to keep them there. In this way, the gods and spirits can still manifest in the Physical Realm, though they tend to do so only briefly.
For a while, this was the whole of the realms.
Then the Great War of Empires occurred, and with it the intrusion of the Outsider. In order to close the Portal and keep the Outsider out, it was decided in council that the world would be Sealed against all such forces — no matter the upheaval and disasters this act might cause.
Unbeknownst to the council, the placement of the Seal around the world did more than block the Outsider’s intrusion. It also accidentally locked in previously free-roaming masses of Dark and Void. Trapped, these two forces settled down ‘below’ the Shadow Realm — not actually physically beneath anything, but bordered on all sides by Shadow just as the Shadow is bordered on all sides by the Physical Realm.
However, while the Umbral Wall stands between the Shadow Realm and the daylit world, there is no true barrier between the Shadow, the Dark, and the Void. Thus, tendrils of the Dark and Void often reach out through the Shadow to touch the Physical Realm — wanting nothing more than to snuff all light and heat and life and magic, and especially break the Seals, so that they can once more be freed into the cold silent blackness of space.
This, then, is the complex mess that Halci’s powers have made for themselves.