Lunia

Lunia, the Silver Heaven, was the first and lowest layer of the plane of Mount Celestia in both the Great Wheel and World Tree cosmologies. It was sometimes called the Silver Sea, after its great ocean.
Celestia's first (bottommost) layer shared borders with the neighboring planes of the Peaceable Kingdoms of Arcadia and the Twin Paradises of Bytopia; travel was possible between Celestia and these planes at certain locations.
Known as the Silver Heaven, Lunia was the first layer travelers encountered. The sky of Lunia was a nighttime sky filled with stars that illuminated the layer with a silver glow. The color pools of the Astral Plane would deposit visitors in the surf of a vast ocean, the Silver Sea, full of clean, fresh water that had the properties of holy water. The sky above Lunia was perpetually dark, filled with beautiful constellations of silver stars bright enough to illuminate the base of the mountain. The dark, starry Silver Sea was full of many good aquatic beings, including celestial whales and sea elves.
The adjacent beach belonged to an island with a majestic mountain decorated with grand citadels made from polished white stone. Descriptions of the citadels varied among travelers leading cosmologists to theorize that there were many of these mountain islands. Also in the surf of Lunia were the portals to the Twin Paradises, Arcadia, and Concordant Opposition which were large, permanent, free-standing blocks of finished stone. Black granite blocks veined with gold led to Arcadia, white granite blocks with veins of silver led to the Twin Paradises, and red granite blocks flecked with blue took you to Concordant Opposition. Travelers merely had to touch a block to activate the portal.
Lunia was the location of a number of godly realms, including Tyr's secondary realm of the Court.

Description

Lunia was a large mountain-island sparsely covered with citadels of white stone, atop white cliffs, and with the palaces of minor deities.[4] Visitors reported different architectural styles for these citadels. Some of the citadels were located on separate islands, some of which were miles long. Trading towns also dotted Lunia, and sea elves from the Material plane were commonly found engaged in trade there.
Some cosmologists considered Lunia something like a subsection of the greater mountain of Celestia; others considered it one of seven separate mountains that were all a part of a single mountain chain. In any case, to reach the next layer/mountain of Celestia, Mercuria, one had to first summit Lunia.
It was always night here, but the dark sky was full of silver stars collectively so bright that a moon was not needed to provide light, and the temperature was like that of a summer's night
Most of the portal connections from other planes came into this layer. Some insisted that this was the only way to enter the greater plane. Most of those arriving by such a means found themselves plunging into a vast ocean of clean and fresh holy water, called the Silver Se or the Silvery Sea, somewhere in the shallower waters near the shore. These waters were salt-free and pleasantly sweet and had the appearance of dark wine. The crashing of the waves on the shore in calm weather reminded some of chimes or the tolling of bells. During stormy weather, the sound was like that of thunder.
The Silver Sea contained all manner of sea life, from schools of tiny silver fishes, to sea elves, dolphins, and celestial whales, to giant creatures of the deep. In calm weather, some of these creatures could be heard singing songs of praise toward the archons. Those who could not swim were quick to be rescued by the zoveri and led to shore—assuming that they were not a kind of creature harmed by holy water. Being submerged in this ocean was enough to annihilate all except the most formidable beings harmed by holy water.
To reach Lunia with the plane shift spell required a gold planar fork tuned to the note of D

Government

Barachiel Barachiel, the ruler of Lunia.
The ruler of Lunia was Barachiel, one of the celestial paragons of the archons. He commanded all of Celestia's forces against attacks on the sacred mountain, though these rarely occurred. He reigned from the Citadel of Stars.
Lunia was divided into 196 provinces, each with a throne archon serving as governor. These 196 thrones reported through the hierarchy up to Barachiel. The defense of Lunia was ensured by the host of hound archons.

Locations

The largest trading center of Lunia was known as Heart's Faith, located not far from a portal from the Outlands. It was built into the side of a cliff and was ruled by a powerful lammasu and his harem. The town had a central plaza that flooded at high tide to serve as a harbor for travelers.
Besides Heart's Faith, another well-known complex was the Fortress Eternal and Everlasting. Barachiel's palace, the Citadel of Stars, was located on the shore of the Silver Sea.
One of the castles found on the shore of Lunia was the home of an evil wizard trying to reform his ways. Castle Mahlhevik was built with full permission from the archons of Lunia
Far out in the Silver Sea was found an abandoned tower known as the Tower of Fire. Powerful magic prevented anyone from flying to the tower; the only way to reach it seemed to be by water. The purpose of the tower was unknown, but the place was filled with an eerie blue fire that was very hot but caused no harm. The rooms of the tower seemed to shift and change without reason, though some claimed that there was a yet-to-be-discovered pattern to this.
Realms One of Tyr's domains, the Court, was located here.

Inhabitants

Besides the many varieties of sea creatures living in the Silver Sea, Lunia's primary inhabitants were the lantern archons, the petitioners of the deities of The Triad. Hound archons were also present in considerable numbers, as they had the two jobs of greeting guests to Lunia and keeping watch over the lanterns.