Arx Infinitus

Arx Infinitus is a demiplane floating in the Deep Ethereal sealed away from intruding access by powerful abjuration magic. The Codex Keepers have studied the Codex of the Infinite Planes long enough to have gleaned some of its defensive secrets, and while they cannot keep the bearer of that powerful artifact out, nearly all other intruders are barred from accessing the demiplane.

The demiplane is about 5 miles across in a sphere shape. In the center floats a magnificent stone and silver fortress, the Citadel of Arx Infinitus, with dozens of spires rising up from the halls and buildings of the main structure. It floats on an island of earth in breathable air, and a picturesque landscape of breathtaking mountains and beautiful vistas surrounds this center island. It is all an illusion, however, cleverly painted on the interior “walls” of the demiplane to give the impression of a vast and gorgeous landscape.

Dozens of smaller islands, most only 30 feet across, float around the central citadel roughly at “ground” level with the building. These smaller islands contain grass, rocks, and other natural features, and many scholars of the Codex Keepers spend their days in contemplation among them. Each island can be “piloted” by force of thought, though at a slow pace, allowing for drifting and moving among the quiet air.

Three larger islands are anchored closer to the entrance to the citadel. These islands each contain a special teleportation circle that members can use to travel outside and return safely. The sigil sequence of each circle changes on a regular basis to prevent access from getting out to the wider multiverse, and protective wards keep first time visitors enclosed in force cages until dealt with by a planar or master sage of the citadel.