With procedurily-generated artifacts scheduled to be worked on by Toady One after he finishes with job priorities and taverns I thought that it might be an appropriate time to bring up the idea of super-artifacts.
The basic premise would be something like in every world during world gen there (in addition to the future regular artifacts) could be generated 1 or 2 super-artifacts that are immensely powerful, potentially dangerous or difficult to use and are woven into the mythology/cosmology of the world in ways that make them widely known but many regard them just to be myths. They would be extremely difficult to find, likely requiring multiple sites to be travelled to along with puzzles and deadly monsters to vanquish.
Examples from history and earthly mythology/religion include the hammer of Thor, Pandora's box, the book of Thoth, the Holy Grail, the thunderbolts of Zeus and the well that Odin drinks out of to become wise. These super-artifacts could be items, weapons or even large objects like the previously mentioned well. Using or activating these super-artifacts could cause player-based effects such as necromancer-style immunity to bodily needs, or could even have effects that change the whole world such as unleashing a flood of monsters, transforming the landscape, or even destroying the world (part of the risk of using a super-artifact which purposes are unknown).
Of course it would make more sense to broach this topic once procedurly-generated mythology is worked on more with randomized creation myths and struggles between deities and so forth as this would give a proper context for the super-artifact (although it wouldn't be nescecary). But even without this the framework for them could be implemented alongside world gen of regular artifacts pretty easy.
They wouldn't even have to be accessible at first, until the means to reach them is implemented into the game, initially only viewable in legends mode. They could all be located on distant islands, castles in the sky, under the sea, in the land of the dead and other similar places. It would just be cool to eventually be able to search for and interact with super-artifacts that are more then just a named masterwork-weapon embedded with zebra bone and tourmaline. The search for the Golden Fleece is one example that comes to mind. They could often be almost impossible to reach but every now and then it would be very epic to go on a long adventure spanning the globe in search of the most important and revered/mystical/feared object of all time.
If anyone has any thoughts on this or ideas feel free to share.