The party has a Prison of Zagig, I would count that as a minor artifact.
Otherwise, their magic is the appropriate +3 ring, +4 cloak, +3 plate mail, +4 sword, +3 dagger, +3 mace, bag of holding, AC 2 brancers, wand of frost, cube of force, pearl(s) of power, ring of wizardry, robe of the...