Onyx

Used most often by the entities of Aren and Cien, Onyx is a building material that creates a similar effect to one-sided glass. Instead of the non-glass surface acting as a mirror, it is lustrous opaque black.
Later adaptations thereof, such as the apartment buildings in Roen, are also photovoltaic cells and collect solar energy. Older versions, such as the Wall dividing the Entities and the Onyx Building in Aren, are just one-way glass and do not collect solar energy.

Uses

Aren

The Onyx Building is the tallest building in Aren, and is panelled entirely in Onyx. The darluces are paneled in Onyx, allowing for a 360-degree field of vision. Additionally, newer models are plated in the photovoltaic version of Onyx, preventing them from ever needing a recharge.

Cien

Juno refused to panel buildings in Upper Cien with Onyx, as she valued transparency among her citizens. However, Onyx is oft-employed in Lower Cien by the Commander.

Eden

Eden has hundreds of "peepholes," which are large windows that allow spectators to view the biomes inside. Some function as doors, and subsequently allow for Ernesto Castillo to enter and hunt the inhabitants.

Roen

Most of the billboards are made of Onyx; as are most apartments. Individual rooms to submit decade achievements are paneled with Onyx, allowing for a judge to look in. All are equipped with photovoltaic cells.

General

The Wall dividing all four Entities. Not to be confused withe the Aren Wall, which is inside of the main Wall and made of simple brick.