First Appearance: Incredible Hulk #377 (January 1991).
Appearances: Incredible Hulk #377-426.
Years Active: Centuries.
The Pantheon are a group of super-powered and extremely long-lived beings who have existed, in hiding, for centuries. At some point in the distant past, perhaps more than a thousand years ago, a being named Vali, who may or may not be a child of the Norse god Loki and the sister of Hela, struck a deal with the alien race the Troyjan. In exchange for (if I recall correctly) a tribute of flesh (offering up his children to the Troyjan) the Troyjan gave Vali greatly elongated life.
(I think. It's been a long time since I read the issues.)
Over the centuries Vali, who began calling himself Agamemnon, fathered various superpowered children and adopted others, all of whom took on names styled after legendary Greek characters (Ajax, Achilles, etc). Agamemnon and his children, who called themselves the "Pantheon," stuck to the shadows, doing good works from various secret bases. In the modern era they revealed themselves to the Hulk and recruited him, but his association with them ended badly, with Agamemnon turning against the Pantheon and the Hulk, the main Pantheon base being destroyed, and Paris, the new leader of the Pantheon, swearing vengeance against the Hulk.
Note: There's a hint, in one of the issues, that Vali was Bucky (I). This was a PADian joke and is not to be taken seriously.