The great legendary king and hero Ulysses (the Latin variation of the Greek "Odysseus") appears in canto 26 of Dante Alighieri's Inferno. Ulysses is being punished in the eighth bolgia (Italian for "ditch," also known as "pouch") of the eighth circle of hell, where the evil counselors receive their life's just desserts.
Ulysses is engulfed in an eternally-burning tongue of flame which he shares with Diomedes, the commander of the goddess Athena's warriors. Ulysses and Diomedes, both of whom are mythologized in Homer's Odyssey, share the punishment of those who used their tongues to deceive others.
According to Virgil, Dante's guide through hell, Ulysses is condemned to this deep circle of hell for his three greatest sins:
And there within their flame do they lament
The ambush of the horse, which made the door
Whence issued forth the Romans' gentle seed;
Therein is wept the craft, for which being dead
Deidamia still deplores Achilles,
And pain for the Palladium there is borne.
(canto 26, lines 58–63)
Ulysses is responsible for the deception caused by the Trojan Horse, the large wooden horse that Ulysses had built as a gift for the Trojan people but which actually contained a small force of Greek soldiers. When the Trojan soldiers were asleep, the Greek soldiers emerged from the horse and opened the gates of Troy to the Greek army, who destroyed the city and thereby ended the ten-year Trojan War.
Ulysses's second great sin was to induce Achilles to join the Trojan War, which caused Achilles to abandon Deidamia, his mother, who dies from sorrow fearing—and her fear is borne out—that Achilles will be killed in Troy.
The third sin for which Ulysses suffers the punishment of the eternal flame is stealing the Palladium, which was a statue of the goddess Athena and which protected the city of Troy.
Nevertheless, Dante presents Ulysses as a hero as much as he presents him as a deceiver who is deserving of his punishment. Dante has Ulysses recount another of his heroic adventures, this one with the goal of discovering truth about the world and acquiring a better understanding of "the vice and virtue of mankind" (canto 26, lines 97–99).