Why must Odysseus travel to the underworld and speak with Tiresias?

Odysseus must travel to the underworld to seek guidance from the prophet Tiresias, who can provide crucial information about how to return home to Ithaca. Tiresias offers insights into the challenges Odysseus will face, including the need to appease Poseidon and the dangers posed by the suitors vying for his wife, Penelope. This journey is essential for Odysseus to gain wisdom and foresight, ensuring his safe return and the restoration of order in his household.