Rahi kept in the Archives were held in stasis for safety purposes. Each Rahi was placed inside an inner stasis tube which was surrounded by a clear casing. While in the stasis tube, their life processes were slowed to an extreme degree. They were alive, but not aware, and could remain in that state for thousands of years. Damage to the outer case would not affect the Rahi, but damage to the inner case would cause it to awaken.
A creature kept in a protodermis stasis tube was alive but suspended in time forever. The outer shell of the tube could be shattered without awakening the Rahi within. However, if the inner casing were cracked, the Rahi inside could come to life again and rampage through the Archives. Once a creature was placed in a stasis tube, its life processes would be slowed to a crawl. Outer shells could take all kinds of pounding, but if the inner shell of a stasis tube cracked even a little, the rush of air would wake up the contents.
Stasis tubes were used in the Archives to keep Rahi in suspended animation so they could be studied. The clear casing was made of crystal.