Demiplanes

This catchall category covers all extradimensional spaces that function like planes but have measurable size and limited access. Other kinds of planes are theoretically infinite in size, but a demiplane might be only a few hundred feet across. There are countless demiplanes adrift in reality, and while most are connected to the Astral Plane and Ethereal Plane, some are cut off entirely from the transitive planes and can only be accessed by well-hidden portals or obscure magic spells.