Within a developed Pagan religion, there is often a presentation of cosmological concepts. Not to mention an enumeration of worlds. Though the number varies in various Indo-European cultures, three is a very common number. John Shaw, in ‘On Indo-European Cosmic Structure’ covers this very well. (The link I shared is to academia.edu, free to sign up, and many articles are free as well.) In Celtic lore, namely Irish, the concept of a Land-Sea-Sky division of worlds is present. In this case, the Sea is the Lower World, the Sky is the Upper World. There’s no absolute proof about the veracity of this in a Gaulish context. However, given that many other cultures had a three world cosmological structure at their core, it is not a stretch to assume this to be the case with the Gaulish peoples.
In Tegoslougos Nemotarvos, we hold to a three world structure as well. Those three worlds are Albios, Bitus, and Dumnos. A bit of explanation is required, though it should be noted that I am far from the first person to come to this conclusion.
Dumnos is the Underworld, the Deep, and can relate not only to Mori (Gaulish for “sea”) but that which is under Bitus (the world in which we live). Under lakes, streams, caves, you name it. That which is under the Earth, home to Andernados (chthonic) beings. This includes not only Dêwoi (Gods) of Dumnos, but at least some Senisterî (Ancestors), and other spirits. Some benevolent (bestowing riches and fertility of the land), others malevolent. It is here that is the womb of the Earth, as we come from it, and our bodies, at the very least, return to it.
Dumnos is associated with things Giamos — that is, darkness, chaotic, chthonic, primal, and of winter.
Bitus is our own world, which other than being the home of humanity, is home to a myriad of other beings. This is also the domain of the Talamondêwoi, which are Gods and Spirits of the Earth. This includes deities tied to locations such as lakes, rivers, mountains, trees, forests, and at this point, if not before, cities. Bitus is acted upon both of the other worlds. Thus we get both order and chaos, to live and die, the turnings of the seasons, and influences from both of the other worlds. We are subject to the full experience of these cycles.
Albios is the upper world. It is home to Uerandos (celestial) beings. The Gods and Spirits of Nemos (the Sky), live here. Generally, these are the beings that provide order, protection, and that which is needed for civilization. To simply classify them as benevolent or malevolent does them a bit of disservice, as it is their job to preserve order. However, through reciprocal exchange with Them, as with the Gods of the other two worlds, They too, may return such gifts with Their benevolence.
Albios is associated with things Samos — that is, light, order, celestial, civilized, and of summer.
One can also posit something that links the Three Worlds. That would be Bilios (the World Tree). Bilios is, in this case, the axis mundi, or pillar of worlds. In this case, comparisons can be made to Yggdrasil in Norse mythology, or Mount Olympus in Greek mythology. The roots of Bilios lie within Dumnos, the trunk in Bitus, with a canopy that stretches to Albios. At the least, reflective of the beliefs of Tegoslougos Nemotarvos.