Sumtu (Sone-Tu) is a Southern Chin (Tibeto-Burman) language spoken by about 28,000 people in Rakhine (Arakan) State, Myanmar. Ritual Sone-Tu, is a ritual form of Sone-Tu, known only by three spirit mediums who are now in their 70s or 80s. During pre-colonial times, Ritual Sone-Tu was understood by the wider community and used in rituals and festivals. The arrival of Christian missionaries during colonial times caused widespread decline in ritual practices. The encroachment of the Rakhaing and Burmese languages on the Sone-Tu lexicon have meant that Ritual Sone-Tu is now completely untelligible to Sone-Tu speakers. Ritual Sone-Tu will disappear with the last three surviving spirit mediums.