Nyx

Nyx is an endless plane of existence where the powers of potentiality and belief hold sway. It is the realm of the gods, of belief given form, of dreams, and of rising and fading philosophies. From here, the pantheon of Theros watches the mortal world and guides the living. Though the gods live in a veritable paradise, they can’t sever themselves from the mortal world. To do so would be to lose the faith of their followers, the source of their magic and a power they will not relinquish. Nyx can be perceived in the night sky, with its ever-changing brilliance marked by constellations and cosmic phenomena. Its power slips into the world in the same form, with star fields filling the shadows of Nyxborn beings that are infused with its power.
While Nyx is impossible to map, distinct regions do exist, and some travelers have returned to the mortal realm with tales of these incredible locations.

Geography

Mount Hiastos This drifting mountain rises in sharp relief against the starry sky of Nyx, culminating in a golden orb that can be seen from a great distance. Some speculate that this orb is the source of Nyx’s vibrant colors and lights, and that without it, the plane would be plunged into eternal darkness. Several gods make their homes on the mountain’s slopes. Heliod maintains a sprawling palace of gold and white marble, with a rooftop throne where he receives guests. Purphoros maintains a forge beneath the mountain, where he crafts philosophies, energies, and creations that would be impossible to manifest in the mortal world. Keranos lives near the summit of the mount, where he sends lightning bolts of inspiration to manipulate forces throughout dreams and the cosmos. Nylea, too, is known to visit Mount Hiastos, maintaining a sanctuary there within an ancient, knotted wood.
Mystic Sea This body of mist and water hides endless secrets within its depths—both literal secrets that manifest from mortal minds and unimagined concepts not yet fully formed. Thassa’s palace floats underwater, its buildings suspended in giant bubbles that drift with the currents. At its edge, in a city of divine copper and marbleized hopes, Ephara makes her home.
Tovian Fields Nyxborn legends battle here in ceaseless, glorious war. Unlike any mortal environment, the Tovian Fields are an expanse of energies, the clash of opposing philosophies manifesting as throngs of legendary combatants. In the midst of this riot rise the palatial war-tents of Mogis and Iroas, who lead the endless battle.
Kruphix claims the borders of the Tovian Fields as his territory. He doesn’t maintain a central residence. Rather, his influence binds the conflict, encompassing all perspectives and preventing the battle from spilling forth into the rest of Nyx.