The planes of Calcaria are not well understood among mortals, definitely not among the common-folk. Some scholars have gone to great lengths to study them, and even fewer have travelled to the inner and outer regions of the Aeternum. The work left behind by these academics has been studied and re-studied over aeons, few daring to tread where they have.
"The Astral, as terrifying as it is beautiful." Some random ass dudeThough not often travelled, the Inner Planes are better understood than the Outer, which are considered the domains of the gods and not to be trifled with. Adventurers, scholars and wizards sometimes make perilous journeys into the inner regions however, such as the Elemental Planes or the City of Secrets, if their need is dire.