Demirealms, sometimes called "demiplanes" or "subealms", were ill-defined planes of unusually small size that existed either within other Realms or outside the known cosmology entirely, depending on which cosmological model was used. They were typically, if not always, of finite size and were always extradimensional spaces. Earlier scholarship considered demirealms to be planes still in the process of formation, unfinished in some fundamental sense; more modern sources treated the category as a catch-all classification for planes of generally measurable size and limited access, sometimes so limited that even the Ethereal or Astral Borders could not reach them, save from specific points in other Realms.
Conditions within a given demirealm varied enormously, with no two places guaranteed to share the same physical or magical properties.
They could occur naturally, but the great majority were created deliberately, either by deities or by powerful Spellcasters, often through rituals of a genesis-like nature. Some demirealms that touched the boundary between the Ethereal Border and other planes were marked by portals of consistent and distinctive coloration.
Their placement within cosmological models depended heavily on which framework a given scholar favored. Under the Cosmic Wheel, demirealms were generally held to have no fixed place among the Realms, existing instead as pockets that could be tethered to almost any point in the multiverse. Some models placed the bulk of known demirealms within the Outer Realms, while others considered them to exist entirely outside the Outer Realms and transitive planes alike, tethered to the wider cosmology only by leylines or by the will of their creator.
Certain planes had contested status, classified as demirealms by some scholars and placed in other categories entirely by others; such disputes were common and rarely resolved to universal satisfaction. A number of these places, such as those of the Bloomtides or Gloomshrouds, were known only by rumor, referenced in fragments of lore, secondhand accounts, or the records of secretive organizations, with little corroborating evidence as to their true nature or location.