The Holy Grail is said to be one of the most infamous and sought after of arcane holy relics.
According to Christian doctrine, the Grail is the cup used by Jesus Christ during the Last Supper. It is also the recepticle that caught Christ's blood during the crucifixion at Golgotha.
The origins of the Grail diverges:
1) The Grail date back to the time of the first Ice Age and the waning years of Neanderthal man. A Neanderthal shaman named Rheelai was one of the first of his kind to master the art of metallurgy, and forged the Grail out of solid gold. Rheelai and his tribe were slaughtered by a clan of Cro-Magnon warriors and they took possession of the cup.
2) The Grail was one of the Seven Imperishable Treasures. Following the fall of a "proto-Camelot" 10000 years ago, the ruins of the city were taken over by the Sheeda and their evil leader Mordred the Dead. Seeking a weapon that might drive Mordred out of their lands, the surviving knights, Bors, Peredur, and Galahad aided the Dwarrow men (dwarves) to construct an artificial Holy Grail - essentially a primitive version of the atomic bomb.
The Grail was not seen again until the time of Jesus in the early 1st century AD. Some thirty or so years following the death (and apparent resurrection) of Christ, Joseph of Arimathea allegedly took possession of the Grail and it was believed to have been housed somewhere in Glastonbury Tor.
The Grail surfaced again around the 6th century AD when Sir Justin Arthur delivered it to Arthur Pendragon, King of the British land known as Camelot. The Grail became a powerful tool in defending Camelot against the forces of the evil Morgaine le Fey. It is possible that immortal conqueror Vandal Savage may have learned of the Grail at this time as he was alive and present in Camelot in the years leading up to its fall.
Vandal Savage was the mastermind behind the Illuminati, whose primary objective was to take possession of various mystical artifacts such as the Grail and the Spear of Destiny. Fringe elements of the Illuminati, including the Knights Templar and their later successors the Order of the Rosy Cross devoted their lives in search of the Holy Grail. 
It is believed that the Grail may have been brought over to the United States during the late 18th century. Vandal Savage and the Illuminati took a special interest in the actions of Colonial General George Washington, and even attempted to assassinate him.
The Holy Grail turned up again centuries later during World War II. On December 8th, 1941, the Dragon King delivered the Grail to Japanese Emperor Hirohito and his Shogun Tojo. Channeling the power of the Grail, the Dragon King was able to project a sphere of energy that would ultimately corrupt any mystical or metahuman invaders, insuring the safety of the Japanese Islands and their conquered territory from threats by the super-hero community.
The current whereabouts of the Holy Grail are unknown.
- The Holy Grail is also an important relic featured in the non-continuity Camelot 3000 maxi-series.
- The Holy Grail was used by a group of goddesses, composed of the matriarchal oracles of each pantheon, to create a new race. The goddesses poured their godly essences into the goblet, so that their energies would mingle, and each goddess drank a sip of the resulting liquid. Afterwards, they split up to find consorts and give birth to the new race. Hera's Amazons and Frigga's Valkyries are the most notable representatives of that new race.
- Surviving members of the Neanderthal tribe who first created the Grail evolved into the Yeti, who in turn, crafted a second Grail. However, it is assumed that most stories relating to the Holy Grail correspond to the first Grail crafted by Rheelai.