Zeus in his wrath denied men the secret of fire. Prometheus felt sorry and watched as they shivered in the cold and winter's nights. He took fire from the hearth of the gods by stealth and gave it to man as a gift. Thus mankind was warm. To punish Prometheus for this hubris, Zeus had Prometheus carried to Mount Caucasus, where an eagle by the name of Ethon would pick at his liver; it would grow back each day and the eagle would eat it again. About 12 generations later, Heracles, freed Prometheus. Prometheus was invited to return to Olympus, though he still had to carry with him the rock to which he was chained.
(Adapted from Wikipedia)
 

 Titan! to thee the strife was given
 Between the suffering and the will,
 Which torture where they cannot kill;
 And the inexorable Heaven,
 And the deaf tyranny of Fate,
 The ruling principle of Hate,
 Which for its pleasure doth create
 The things it may annihilate,
 Refus'd thee even the boon to die:
 The wretched gift Eternity
 Was thine--and thou hast borne it well.
 …
 And in thy Silence was his Sentence,
 And in his Soul a vain repentance,
 …
 Thy Godlike crime was to be kind,
 To render with thy precepts less
 The sum of human wretchedness,
 And strengthen Man with his own mind;
      - Prometheus, Byron, lines 15-25, 31, 32, & 35-38