The Mortal Coil Sound from Master Series. Considered to be one of the most erotically stimulating forms of play, this imaginative sound instrument is made of brushed stainless steel and is designed to increase pleasure. Progressive swells allow for added stimulation. Long and smooth, this sound is perfectly suitable for specific stimulation. Take it to the next level with a little temperature play.. The Mortal Coil can be warmed by warm water or cooled in the refrigerator.