The Shrivenzales were large predators native to Ribos. They had acute hearing and were able to detect ultrasonic sounds. The Shrivenzales slept in the catacombs of Shur during the day and hunted smaller prey on the tundra at night.
The Ribosians kept a small Shrivenzale to guard the crown jewels of Shur during the nighttime. Garron and Unstoffe used drugged meat to render it unconscious while they placed a lump of jethrik - which was actually a piece of the Key to Time - in with the crown jewels as part of their con. (TV: The Ribos Operation)