Sigmund Freud's death instinct, first defined in his book Beyond the Pleasure Principle, and named after the Greek personification of Death (see above writeup). This death instinct is the very essence of destructive instincts, because it links every desire of aggression and of sex with the desire for death. The aim of this instinct is to undo connections and destroy things. It is the instinct associated with the desire for pain, for hurt, for corruption and destruction. Basically the opposite of Eros, this instinct is, according to Freud, the reason for all our aggressive tendencies.

Freud makes a note at the conclusion of his book Civilization and its Discontents that human beings, following Thanatos, have invented the tools to completely exterminate themselves.

Just as to Eros belongs Libido, to Thanatos belongs Destrudo.