The wrist device was a piece of technology of Silurian design. They were worn by Silurian leaders and served as a way of controlling as well as charting the progress of a Myrka when it was set loose. They had several buttons and were worn on the left arm. They were capable of telling the wearer if the Myrka was successful or if it had been destroyed. Scibus, a companion of Icthar, wore one such device which was used to control the Myrka set to storm Sea Base 4. (TV: Warriors of the Deep)