The linking chamber in Haven, which is made of Nara
Nara was a type of metallic gray stone with thirty times the density of steel, and was the hardest stone known to the D'ni. It was invented using fusion-compounding technology in 5307 DE (2350–2349 BCE) by the Guild of Guild of Miners and Guild of Stone Masons. The material was produced by reconstituting naturally-formed stone in the fusion-compounder, a machine that reforged the atomic links of the rock, reducing its volume by a factor of 200. The resulting Nara would be formed into cylinders, which would later be melted down and molded as desired.
Atrus wrote the Linking Chambers in Haven and Spire out of Nara to prevent his sons from destroying them. Sirrus, however, succeeded in developing a way to shatter the cages via molecular disruption using his Crystal Bombs.