Nyx

A paranormal realm associated with dreams and the subconscious, it is a literal and proverbial night sky where the gods dwell. Nyx is so closely tied to the plane's deities that, whenever they manifest, where they should be shadowed they instead display the glorious starlight of the night sky. Dreams are seen as gifts from the gods, and so are enchantments, due to their connection with this realm; whenever mortals sleep, they are said to be "visiting Nyx". Tales of the gods can be seen played out in the constellations.
Besides the Gods, Nymphs are also formed/dwell in Nyx, as do some Archons and celestial versions of earthly creatures like Elks and Crabs. All dwellers of Nyx are living enchantments, formed from the collective subconscious and by the divine will of the gods. Creatures born in Nyx are referred as Nyxborn, and their numbers have increased in recent years, as the boundaries between the night sky and the living world decreased. The Gods, Nyxborn, and other items forged from Nyx are infused with Nyx, so that the night sky appears intertwined with their physical form.
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.

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 Field

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.