The World of the Ortegids

The setting of the Erdrick Trilogy has some very interesting worldbuilding implications. Not all of them were intentional - some appear to have been invented as a means to justify game mechanics and engine limitations - but if one was to run with them, it would produce some intriguing opportunities at the tabletop. For The Saga of the Ortegids, I've decided to interpret the setting as looking something like this, in order to best take advantage of these implications:

Erdland: The outer surface of a hollow planet, which behaves as a typical Earthlike planet would. Has a sun and moon and a normal day-night cycle. I've chosen to go with a geocentric interpretation here, mainly for symmetry with Torland. Very much a History's Greatest Hits-type setting in the vein of the Hyborian Age; the land masses correspond roughly to those of Earth, and the cultures and civilizations parallel those of the appropriate regions, though not always contemporaneous ones. Notable locations include the Kingdom of Aliahan, the Romalian Empire, the islands of Zipangu, Dharma Abbey, and the deserts of Isis. The majority of Dragon Quest III takes place here.

Torland: The inner surface of the hollow planet, with its own oceans and land masses. It is lit by an artificial inner sun, causing it to be in a constant state of twilight (this, incidentally, is because they hadn't figured out how to do a day-night cycle in the first two games, and rather than admitting that like a normal person, decided to go full Burroughs). The geography is invented; culturally, it seems to be vaguely Norse. It was said that demons, dragons, and monstrous races originated from Torland (compare Alexander's Land of Darkness), though most of them have established native populations in Erdland. Likewise, humans have settled Torland and established their own kingdoms there, including Alefgard, Rhone, and the three Ortegid kingdoms of Lorasia, Samartoria, and Moonbrooke. Dragon Quest I, II, and the latter third of III take place here.

Zenithia: A small floating island located in the clouds above Erdland. Inhabited by a magically advanced civilization of winged people, who dwell in Castle Zenith. At the summit of the Castle dwells the Divinegon, an immortal god-dragon who will grant one wish to anyone who can impress him in battle. Zenithia doesn't play a role in the games' story until IV, V, and VI (the "Zenithian Trilogy"), which are not explicitly canon to the Erdrick Trilogy and are thus outside the scope of this project, but it was added as a bonus dungeon to later releases of III, so it makes the cut.

The Pit of Giaga: A massive chasm in the earth linking Erdland and Torland, located at the caldera of a volcano in the Southlands of Erdland. Previously the only means of travel between Erdland and Torland; descending from the Pit in Erdland would cause one to fall out of the sky in Torland. It was sealed off after the events of Dragon Quest III, but no one can say how long that will last...

The Worldtree: A massive tree linking the three realms of Erdland, Torland, and Zenithia. It grows over the course of every Age, periodically wilting, crumbling, and regrowing. By the time of Dragon Quest III it was only a sapling, and we don't see it again in the Erdrick Trilogy, though similar features have appeared in other games. For the purposes of The Saga of the Ortegids, the Worldtree has grown to its full strength by the modern era, and serves as a means to traverse the three realms. Its mountain-like roots jut out of the ground in Torland, and one can follow them up into Erdland and Zenithia, or descend the trunk, which grows in the continent-spanning Worldforest of Erdland, into Torland. This has allowed for travel and trade between the different realms, though the locals of the different worlds have been slow to accept the sudden contact with other lands.