Who is the shadow in odyssey?

In Homer's _Odyssey_, the shadow is the shade of the dead Greek warrior Achilles. Odysseus encounters Achilles in the underworld, Hades, where he learns that Achilles is still as fierce and competitive as he was in life. Achilles is eager to hear news of the world above, and Odysseus tells him of the Trojan War and its aftermath. Achilles' ghost also gives Odysseus advice on how to return home safely.