The Nevinyrral's Disk is an artifact from Magic: the Gathering collectible card game (the cash cow that generated the money for the WotC to buy D&D franchise...):



This object has a "peculiarity" that makes it quite "arnesonian", i.e. its name is the reverse spelling of a real person (Larry Niven) that somehow helped developing the game.

It has also a more literary resonance: it is an artifact from a long lost past, that has the power to halt and erase a section of a story ( ) by destroying completely one major part of the world and all its history.
Confidentially, it sounds a bit what happened during Blackmoor's last days... do you think that a similar artifact could feature as a trigger for the Rain of Fire events with some credibility?

BTW I once used a similar object in a "pocket-sized" sub-campaign Ravenloft-style (i.e. the adventurers are transported in a "strange" situation, where they have to complete some kind of quest / solve some kind of puzzle in order to get out of the demi-plane in one piece), where the solution of the quest in the demi-plane includes triggering an artifacts that progressively (and quite quickly) destroys the demi-plane as well.

Now that I think about it, even the Golgothian Sylex (), still from Magic: the Gathering, would do the same service...