The Grand Vivarium is a major Seal of the the Verdant Mother, guarded by Rydess and her mother before her. It is deep below her Lair, under the mountain in the western portion of the Watchers' Island.
Originally, the Vivarium was build by the local Dwarves, as a feat of ecological ingenuity, and in veneration of the Mother. The Dragons twisted the place into a prison, and sealed her there instead.