Prometheus stole fire from the forge of Hephaestus (Vulcan) and gifted it to mankind. Zeus was angered by this betrayal as he considered fire to be only for the gods. As a punishment to Prometheus, his innards are eaten out every day by Apollo's Eagle, and then they would grow back, so they could be eaten out the next day. The concept was to capture what that very first day of knowing your fate would be like.
Hephaestus (Vulcan) binds Prometheus to the rock that will be his permanent home as Apollo's Eagle looms overhead.