How does Heather McHugh use imagery in Three To's and an Oi?

The imagery can be found in the allusions. An allusion is a reference to an event in history or literature. It can be overtly stated or merely implied. “Three To's and an Oi” contains both types of allusion. The reference to Cassandra is clearly announced in the first word. Readers who are familiar with the story or who look it up when they see it mentioned in the poem can see how the events of Cassandra's life apply to the issues being discussed. It would be difficult to make sense of the first section of the poem without knowing that Cassandra has the ability to foretell her own death and that she cries out in anguish when she knows death is looming.