Shiva Purana
एतस्मिन्नंतरे दैत्यो मूकनामागतस्तदा ॥ सौकरं रूपमास्थाय प्रेषितश्च दुरात्मना ॥ १० ॥
After this a demon named Muka arrived He assumed the form of a snake and was sent by the evil spirit.
english translation
etasminnaMtare daityo mUkanAmAgatastadA ॥ saukaraM rUpamAsthAya preSitazca durAtmanA ॥ 10 ॥
hk transliteration by Sanscript