And there the children of dark Night have their dwellings, Sleep and Death, awful gods. The glowing Sun never looks upon them with his beams, neither as he goes up into heaven, nor as he comes down from heaven. And the former of them roams peacefully over the earth and the sea's broad back and is kindly to men; but the other has a heart of iron, and his spirit within him is pitiless as bronze: whomsoever of men he has once seized he holds fast: and he is hateful even to the deathless gods. Hesiod Theogony
Euphronios Krater, Hermes (Psychopompos) in the Middle with the twin brothers Thanatos and Hypnos (Death and Sleep) moving Sarpedon, the son of Zeus to Hades the world of the dead. Calyx-krater, ca. 515 BC; Archaic; red-figure, Metropolitan Museum of Art Signed by Euxitheos, as potter; Signed by Euphronios, as painter, Greek, Attic ( Etruscan Sculpture )
In Greek mythology, Thanatos (θάνατος, "death") was the personification of death (Roman equivalent: Mors). He was a creature of bone-chilling darkness. He was a son of Nyx and twin of Hypnos. He plays little role in the myths. He became rather overshadowed by Hades the lord of death. Night, the destructive, brought forth a horde of villainous immortals. Thanatos was one of that wretched lot.
Night’s offspring are described as "horrible, painful, cruel, brooding, mocking and malignant." (Theogony, 212). (The one exception is "loving Affection" who is placed between Deception and Old Age.)
Thanatos might be poetically called the brother of Sleep and the son of Night.
In art, Thanatos was depicted as a young man carrying a butterfly, wreath or inversed torch in his hands. He sometimes has two wings and a sword attached to his belt.
For let me tell you, Socrates, that when a man thinks himself to be near death, fears and cares enter into his mind which he never had before; the tales of a world below and the punishment which is exacted there of deeds done here were once a laughing matter to him, but now he is tormented with the thought that they may be true: either from the weakness of age, or because he is now drawing nearer to that other place, he has a clearer view of these things; Plato, The Republic
In psychoanalytical theory, Thanatos is the death instinct, which opposes Eros. The "death instinct" identified by Sigmund Freud, which signals a desire to give up the struggle of life and return to quiescence and the grave. This should not be confused with a similar urge/force destrudo.
"Thanatos" is the name of a character in the popular webcomic Bigger Than Cheeses. He is a villain in the Marvel Comics universe as well as the villain in the series T*Witches and the Square Enix video game Seiken Densetsu. The name/concept also appears in an episode of "Dead Like Me" (Season 2).
Mars is not the Roman equivalent of Thanatos. Thanatos is death. Mars, the god of war, is Ares' Roman equivalent.
San Ildefonso Group, Madrid (Maybe Hypnos and Thanatos, or Orestes and Pylades or the Dioscouri)
Hypnos and Thanatos carry a body , Lekythos, c. 440 BC, D 56, British Museum