The generator crystal for the large shield on Narayan, off (left) and on (right).
Use on Narayan
The crystals from Amateria produce a distinctly powerful effect on Narayan. An electrified crystal emits a resonance which causes water molecules in Narayan's atmosphere to align themselves into an unbreakable shell of ice. The radius of the shell varies depending on the size of the crystal being powered. Atrus took advantage of this behavior to create a secure "airlock" at the link-in point for Narayan by building two ice shield generators of different sizes. In order to unlock the inner shield, visitors would have to enter the Narayani "poems" given to them by Atrus's lessons in the other Ages accessible from J'nanin. This inner shield blocked access to a lower chamber where the J'nanin Book was stored, as well as the Narayani symbols used to spell out the poem needed to unlock the outer shield and gain access to the rest of the Age. After 20 years, though, the inner shield acted as a barrier to accessing the gondola platform as well, since the other doorway has become overgrown with lattice tree roots.
Use on Amateria
While the Amaterian crystal is most effective when used on Narayan, it is still capable of producing a resilient sheet of ice on Amateria as well. Atrus built a semi-circular lathe lined with these crystals, which was capable of generating ice spheres that could travel along a human-sized marble track without breaking. This lathe was attached to the top of the pagoda, which served as the starting point for the track. At the end of it, an acoustic device was used to shatter the ice and allow the rider to access the J'nanin Linking Book.