Shelley frames the poem as a story to make it clear that the narrator hasn't even seen the statue himself. This emphasises how unimportant Ozymandias is now.
"Two vast and trunkless legs of stone"
Emphasises size and stature but also shows that the statue is incomplete.
"Stand in the dessert"
The setting suggests an absence of life and vitality.
"shatter'd visage"
Ironic - even a powerful human can't control the damaging effects of time.
"sneer of cold command"
The sculptor understood the arrogance of the ruler. Links to the power that was once there.
"Which yet survive, stamp'd on these lifeless things"
Having 'survive' and 'lifeless' on the same line hints at how art can outlast human power, but the ruined statue shows that ultimately art can't immortalise power.
"The hand that mock'd them"
'Mock' can mean to ridicule, or to create a likeness of something - perhaps the sculptor intended his statue to make fun of Ozymandias.
"king of kings" / "ye mighty"
Arrogant and powerful - he even challenged other rulers.
"Look"
Having a stressed syllable at the start of the line heightens Ozymandias's tone of command.
"despair!"
Irony - he tells other rulers to 'despair' because of the size and grandeur of his works, but in fact they should despair because their power is temporary and ultimately unimportant, like his.
"the decay Of that colossal wreck"
The ruined statue shows how human achievements are insignificant compared to the passing of time.
"boundless and bare" / "lone and level sands"
Alliteration - emphasises the feeling of empty space in the surrounding dessert.
"stretch far away"
The dessert is vast and survives far longer than the broken statue, emphasising the insignificance of the statue and of Ozymandias.