Stasis Tube

Stasis tubes where what Rahi where kept in at the Archives. In the lower levels, they had broke and the Rahi escaped. After the Great Cataclysm, most of the tubes were smashed and the Rahi escaped. The tubes slowed down the Rahi's life functions to their minimum, keeping them alive but in stasis.

Since the return to Metru Nui and the use of Staff of Artahka, the Stasis Tubes have been repaired and the Rahi will probably be recaptured.

Dark Mirror
In Dark Mirror, Dume was captured in a Statis Tube. Takanuva freed him.