In Greek mythology, Thanatos (θάνατος, "death") was the personification of death (Roman equivalent: Mors), and a minor figure in Greek mythology. Thanatos was a son of Nyx (Night) and twin of Hypnos (Sleep).

In psychoanalytical theory, Thanatos is the death instinct, which opposes Eros. The concept of the "death instinct" was identified by Sigmund Freud. For Freud, Thanatos signals a desire to give up the struggle of life and return to quiescence and the grave. This should not be confused with the comcept destrudo, which is the energy of the destructive impulse (the opposite of libido).

Description

In early mythological accounts, Thanatos was seen as a very powerful figure armed with a sword, with a shaggy beard and a fierce face. His coming was marked with pain and grief. In later eras, as the transition from life to death in Elysium became a more attractive option, Thanatos was seen as a beautiful young man. Many Roman sarcophagi show him as a winged boy, much like Cupid. Thanatos is sometimes depicted as a young man carrying a butterfly, wreath or inverted torch in his hands. He sometimes has two wings and a sword attached to his belt. He appears, with Hypnos, several times on Attican funerary vases, so-called lekythen. On a sculpted column in the Temple of Artemis at Ephese (4th  century BCE) Thanatos is shown with two large wings and a sword attached to his  girdle.

Role

Thanatos, in bringing death, is often followed by the fates of death or Keres, who are called hounds of Hades, and are Death-spirits, devourers of life. Thanatos, they say, is subject to the MOERAE, who are the three sisters who decide on human fate; and as everybody has a portion in life, the individual fate (moira) is usually present when Thanatos comes to fetch a mortal.

Thanatos' power only affects mortals, for the gods, being immortal, cannot be influenced by him. On account of this, Thanatos endures the hate of mortals and the immortals' rejection.

Story

According to the mythology, Thanatos could sometimes be outsmarted. In fact, Sisyphus did so twice. When it was time for Sisyphus to die, he succeeded in chaining Thanatos up with his own shackles. While Thanatos was chained, no mortals could die, but eventually Ares released Thanatos and handed Sisyphus over to him, but Sisyphus tricked Thanatos again by convincing Zeus to allow him to return to his wife. 

Thanatos may come at any time, but his intervention in the case of Alcestis, who died a vicarious death in the place of her husband, is one of his most memorable. For Apollo had obtained a special favour of the MOERAE, which was that when Admetus should be about to die, he might be released from death if someone should choose voluntarily to die for him. Thanatos then fetched Alcestis instead of her husband.  

However, the gods of the Underworld dislike this curtailing and anulling their prerogatives, and consequently Thanatos did not approve of Apollo's manipulations, and called them trickery. And when Thanatos came to fetch Alcestis, Apollo tried to persuade him to wait and grant her a long life. But Thanatos, being ruthless, refused. Heracles  however, took Alcestis from him by force, but later, when his own time came, he could not defend himself