The various planes of existence that make up the planet of Gaion. During the Primal and Divine Ages, there were only two realms of existence separate from Gaion:
Arcia, Aurovi's realm of Light and Celestial Life
Dakia, Denothis' realm of Darkness and Death/Monsters
However, during the Divine Vanishment, T'Nar allowed the output from Aurovi & Denothis' explosion to destroy both realms, the remnants of which he used to rewrite reality and form the realms as we know them now:
The Skies of Hythens - Hytheron's realm
The Aurovian Wilds - untamed realm of life, inhabited by Syna and Jakun
Volsengard - Vulca's realm
Infernos of Chaos - Thatos' realm
The Underworld - untamed realm of death
Cyratia - Cyr's realm
Seas of Akainos - Akana's realm
Fogs of Immoria - untamed realm of space & the mind, an interconnection of the Waria Gaioforce aura that binds the multiverse together
The mortal realm, colloquially referred to as Gaion, stands in the celestial center of these realms.