In the Land of the Dead, Odysseus encounters several significant ghosts. One that troubles him deeply is the ghost of his mother, Anticleia, because when he left home, she had still been alive. Odysseus speaks with many other ghosts and observes still more. His mission in going there—since he himself is still alive—is, per Circe’s instructions, to connect with Tiresias, the blind prophet of Thebes, who can instruct him about his return home.
Tiresias is important because he provides valuable information about the actions and motivations of Poseidon, who, as the ocean god, affects the seas Odysseus must sail. He reveals the source of Poseidon’s grudge against the Achaeans: They blinded his son, Polyphemus.
Tiresias issues predictions and warnings. He correctly predicts that Odysseus will find his home in disorder, and he warns him away from the herds of the Oxen of the Sun that he will encounter on Thrinacia.