Demiplanes can and do exist within the cosmology, forged by powerful magics that unite various aspects to create them. This is due to the presence and will of The Pale, which is ultimately the source of all magic.
Very powerful beings will often create a Demiplane and tie it to a place where the fabric of the Veil is thin or threadbare, worn, and weak.
The Mourae are described as traveling to the demiplane of Mourama within the Pale while sitting on a stone that can float in the air or water. Inside caves, under rocks and under the earth many legends say there exist palaces with treasures. A Moura is a likely a Fell Fae, a Stone Woman, capable of changing shape.
The Elemental Planes are all Demiplanes, and there are a lot of them. The Elemental Planes are exceptionally hazardous for People to enter, for they are realms comprised mostly of that element; crossing into the plane of Stone can prove instantly fatal to anything not able to breathe rock.
The Elemental Planes are Air, Earth, Fire, Frost, Lightning, Stone, Sand, Smoke, Spirit, Sun, Thunder, and Water. Void is a direct conduit to The Void, and often counted as an element, but is not a safe one. Don’t open a passage there elementally. It never ends well. This may be why no spells truly use it – no one has survived the experience, since the caster is always subject to the Void themselves.
Elementals live within the wholeness of their element, and there are birds, beasts, fish, and people that live and exist within them.
Elementals are the total masters of these regions. The Pale is also filled with innumerable pocket dimensions, some lived in, others untouched or unclaimed, but very few ever stumble on one for the Veil hides them as it surrounds them. Gob, Peralda, Djin, and Necksa all make their homes in Demiplanes within the Pale, from whence come the many incredible elemental beings.
Children’s Cycle Teaching
Air births the water, as rain falls into the night.
Water births the earth, as the clay to make our cups
Earth births the fire, feeding on the land
Fire births the stone, clay within a hearth
Stone births the smoke, rising when it burns
Smoke births the lightning, darkening the sky
Lightning births the thunder, shattering our time
Thunder births Spirit, quickening a life
Spirit births the Frost, cooling down a heart
Frost births the Sun, just because it can
Sun births the sand, dust and grains alight
Sand births the air, screaming winds a-sup