What does the phrase "the heart that fed" mean in the poem "Ozymandias?"

The poem "Ozymandias" describes a fallen statue of an Egyptian king that a traveler observed in a desert. The traveler describes how the head and the legs of the statue have broken apart, and the head is partially buried in the sand. Still, from the face, or "visage," of the statue the observer can tell what kind of "passions" the ruler had.  The face has a "frown, / And wrinkled lip, and sneer of cold command,"...

The poem "Ozymandias" describes a fallen statue of an Egyptian king that a traveler observed in a desert. The traveler describes how the head and the legs of the statue have broken apart, and the head is partially buried in the sand. Still, from the face, or "visage," of the statue the observer can tell what kind of "passions" the ruler had.  The face has a "frown, / And wrinkled lip, and sneer of cold command," indicating that he was a fierce tyrant. He had a "hand that mocked them," meaning that his hand was merciless and cruel toward his subjects. He had a "heart that fed." This suggests that he was an oppressor; he took from his subjects more than he gave to them. They were his prey, and he was the predator. We have similar figures of speech about people who use others for selfish gain. We might call someone a "leech" or a "parasite," or we might say someone "sucked all the life out of me" or "drained me dry." This is the sense in which Ozymandias "fed" on his people. The fact that the traveler says it was his "heart" that fed means that his actions proceeded from a wicked and cold heart that was devoid of compassion toward the people he forced to serve him.

The expression "the heart that fed" is both a metaphor and a synecdoche. A metaphor is a comparison that does not use the words "like" or "as." "Fed" compares the oppression of the ruler to a predator feeding on its prey. A synecdoche uses a part of something to represent the whole. You could say you have a "nice set of wheels," but you would actually be referring to your car, not just the wheels. In the same way, "heart" refers to the entire person of the king, not just the organ in his chest. "Heart" is also often considered the seat of human emotions, figuratively speaking, so it bears that additional meaning. Now you can see one of the reasons poetry is so powerful. One definition of poetry is "condensed language." Just four short words can convey a lot of meaning!