If you are open to sceptical questions about Christianity and are not very familiar with ancient Greek literature and mythology you may find the few notes below of interest.
When I first read the following passages (quite some time ago now) I was struck by the way motifs that later became central to Christianity are woven throughout the mythical tales.
After Prometheus had saved mankind from Zeus’s plan to destroy him, Zeus bound him to a rock and ordained an eagle to eat from his liver every day, with the wound healing overnight ready for a fresh dinner the next day — forever.
But a son of Zeus, Heracles, was eventually destined to release Prometheus from his torment.
The poet Hesiod from the 8th or 7th century BCE wrote:
And ready-witted Prometheus he bound with inextricable bonds, cruel chains, and drove a shaft through his middle, and set on him a long-winged eagle, which used to eat his immortal liver; but by night the liver grew as much again everyway as the long-winged bird devoured in the whole day.
That bird Heracles, the valiant son of shapely-ankled Alcmene, slew; and delivered the son of Iapetus from the cruel plague, and released him from his affliction — not without the will of Olympian Zeus who reigns on high, that the glory of Heracles the Theban-born might be yet greater than it was before over the plenteous earth. . . .
The fifth century BCE playwright Aeschylus explained in more detail why Prometheus had to suffer:
However, you ask why he torments me, and this I will now make clear. As soon as he had seated himself upon his father’s throne, he immediately assigned to the deities their several privileges and apportioned to them their proper powers. But of wretched mortals he took no notice, desiring to bring the whole race to an end and create a new one in its place.
Against this purpose none dared make stand except me—I only had the courage; I saved mortals so that they did not descend, blasted utterly, to the house of Hades. This is why I am bent by such grievous tortures, painful to suffer, piteous to behold. I who gave mortals first place in my pity, I am deemed unworthy to win this pity for myself, but am in this way mercilessly disciplined, a spectacle that shames the glory of Zeus.
But Prometheus knew a secret. He knew that Zeus himself was destined one day to be overthrown from his position as chief of the gods. (That particular hero, we elsewhere learn, was destined to be the semi-divine Achilles. But that’s another story.) The mortal Io (who was later to become the mother of the line that produced Heracles) is talking with Prometheus in his misery:
 Ah, you would hardly bear my agonies to whom it is not foredoomed to die; for death would have freed me from my sufferings. But now no limit to my tribulations has been appointed until Zeus is hurled from his sovereignty.
 What! Shall Zeus one day be hurled from his dominion?
 You would rejoice, I think, to see that happen.
 Why not, since it is at the hand of Zeus that I suffer?
 Then you may assure yourself that these things are true.
 By whom shall he be despoiled of the sceptre of his sovereignty?
 By himself and his own empty-headed purposes.
 In what way? Oh tell me, if there be no harm in telling.
 He shall make a marriage that shall one day cause him distress.
 With a divinity or with a mortal? If it may be told, speak out.
 Why ask with whom? I may not speak of this.
 Is it by his consort that he shall be dethroned?
 Yes, since she shall bear a son mightier than his father.
 And has he no means to avert this doom?
 No, none—except me, if I were released from bondage.
 Who then is to release you against the will of Zeus?
 It is to be one of your own grandchildren.
 What did you say? A child of mine will release you from your misery?
 The third in descent after ten generations.
That is, the one to release Prometheus (who was Heracles) was prophesied to be born as the thirteenth generation from the time of Io’s first child.
The god Hermes comes on the scene (it’s not unlike the story of Job with his many “comforters” coming along to chat) and makes another interesting prophecy:
Prometheus’s only hope for an end to suffering is that a god will come to take his suffering upon himself and die in his place.
 I think that by speaking much I will only speak in vain; for you are not soothed nor are you softened by my entreaties. You take the bit in your teeth like a new-harnessed colt and struggle against the reins. Yet it is a paltry device that prompts your vehemence, for in the foolish-minded mere self-will of itself avails less than anything at all. But if you will not be won to belief by my words, think of what a tempest and a towering wave of woe shall break upon you past escape. First, the Father will shatter this jagged cliff with thunder and lightning-flame, and will entomb your frame, while the rock shall still hold you clasped in its embrace. But when you have completed a long stretch of time, you shall come back again to the light. Then indeed the winged hound of Zeus, the ravening eagle, coming an unbidden banqueter the whole day long, with savage appetite shall tear your body piecemeal into great rents and feast his fill upon your liver until it is black with gnawing.
 Look for no term of this your agony until some god shall appear to take upon himself your woes and of his own free will descend into the sunless realm of Death and the dark deeps of Tartarus.
 Therefore be advised, since this is no counterfeited vaunting but utter truth; for the mouth of Zeus does not know how to utter falsehood, but will bring to pass every word. May you consider warily and reflect, and never deem stubbornness better than wise counsel.
This prophecy brings us to our third source, Apollodorus “Mythographus”, or a writer long thought to have belonged to the second century BCE but whose work is now thought more likely to be an early CE provenance. The author wrote a compilation of the Greek myths.
And passing by Arabia [Hercules] slew Emathion, son of Tithonus, and journeying through Libya to the outer sea he received the goblet from the Sun. And having crossed to the opposite mainland he shot on the Caucasus the eagle, offspring of Echidna and Typhon, that was devouring the liver of Prometheus, and he released Prometheus, after choosing for himself the bond of olive, and to Zeus he presented Chiron, who, though immortal, consented to die in his stead.
Chiron was the half-man half-horse (centaur) famous as the great teacher of a host of heroes: Jason, Asclepius, Achilles, Ajax, Peleus. He was famed as the greatest healer, too, but could not heal himself.
On the significance of the “bond of olive” see note #14 on the Perseus site. I have not myself checked all the sources cited in that note.
Earlier Apollodorus had explained why the centaur Chiron was so willing to die to have Prometheus released:
So passing through Pholoe [Hercules] was entertained by the centaur Pholus. . . He set roast meat before Hercules, while he himself ate his meat raw. When Hercules called for wine, he said he feared to open the jar which belonged to the centaurs in common. But Hercules, bidding him be of good courage, opened it, and not long afterwards, scenting the smell, the centaurs arrived at the cave of Pholus, armed with rocks and firs.
Heracles fights off the alcohol-craving centaurs who flee to the cave of the more noble centaur Chiron, but this was not good for Chiron….
As the centaurs cowered about Chiron, Hercules shot an arrow at them, which, passing through the arm of Elatus, stuck in the knee of Chiron. Distressed at this, Hercules ran up to him, drew out the shaft, and applied a medicine which Chiron gave him. But the hurt proving incurable, Chiron retired to the cave and there he wished to die, but he could not, for he was immortal. However, Prometheus offered himself to Zeus to be immortal in his stead, and so Chiron died.
All very “pagan”, of course, but such curiously tantalizing “memes” (as they say today) floating around in that pre-Christian world.
If you enjoyed this post, please consider donating to Vridar. Thanks!