Devil Dance is a misnomer describing the ritual dance performed on the eve of Losar

Losar

Losar is the Tibetan word for "new year." lo holds the semantic field "year, age"; sar holds the semantic field "new, fresh". Losar is the most important holiday in Tibet....

, the Tibetan

Tibetan people

The Tibetan people are an ethnic group that is native to Tibet, which is mostly in the People's Republic of China. They number 5.4 million and are the 10th largest ethnic group in the country. Significant Tibetan minorities also live in India, Nepal, and Bhutan...

 new year . The actual name of the dance is Chhaam which is performed with elaborate costumes and masks. This dance is done to commemorate the assassination of the cruel Tibetan king, 'Langdarma

Langdarma

Langdarma was the last emperor of the unified Tibetan empire, who most likely reigned from 838 to 841 CE. Early sources named him Tri Darma meaning "King Darma"; "Lang" is a nickname meaning "ox". He was also called tsenpo or lhase Au Dunten...

' in the 9th century CE

Common Era

Common Era ,abbreviated as CE, is an alternative designation for the calendar era originally introduced by Dionysius Exiguus in the 6th century, traditionally identified with Anno Domini .Dates before the year 1 CE are indicated by the usage of BCE, short for Before the Common Era Common Era...

. So it actually a dance symbolising the victory of good over the evil.