Feed the artifacts to a Paragon Sanctified Umbral Half-Celestial Bag of Devouring of Legend (They're creatures, so adding templates should be valid)
Each artifact fed to it adds another template, related to the artifact's abilities. It has been used to dispose of artifacts before, hence the added templateage.
So now the PCs have an objective. Sounds easy enough, right? It won't be - the bag's going to want to eat them as well, and if they try to toss in the artifacts and run, it'll just make it stronger.
In game terms the bag would be known as something like the "Maw of the Ancient", said to have existed before the gods themselves, which gluts itself upon powerful magic.
Give it a companion in the form of living spell: Mordy's Disjunction, and you're good to go.