Deuteronomy refers to a Kingdom of Fierce Countenance: "The LORD shall bring a nation against thee from far, from the end of the earth, as swift as the eagle flieth; a nation whose tongue thou shalt not understand; A nation of fierce countenance." Deut 28:50

Various Evangelical commentaries confirm that this is the Roman Empire. Thus, the King of Fierce Countenance in Daniel 8 refers to the Kingdom of Fierce Countenance in Deuteronomy 28.