What is the poetic device used in the line "My name is Ozymandias, King of Kings"?
Interestingly, this single line uses at least four poetic devices. The two sound devices that are most prominent in the line are alliteration and consonance. In the phrase "King of Kings," the initial consonant /k/ sound is repeated, which is alliteration. The words "Ozymandias" and "name" both contain the /n/ and /m/ consonant sounds, but not at the beginning of both words. Repeating internal or end consonant sounds between words is called consonance.
The other two poetic devices relate to "King of Kings." First, this term is an epithet. An epithet is a descriptive term used in place of or alongside of a person's name to characterize the person, often in a positive or negative way. Here the great king chose this epithet as a way to describe his prominence among rulers of his day.
"King of Kings," besides being an epithet, is also hyperbole. Hyperbole is an exaggeration for effect. Although the king claims to be the the king of [all] kings, that was certainly not literally true, or he would have been ruler of the entire world. He chooses to exaggerate his role among other nations as a way to establish his greatness.
Lastly, one could consider whether personification is used here because the statue is speaking. However, because the king had his own words inscribed on the pedestal, this does not really count as giving human qualities to an inanimate object.