Change the Knight quest artifact to be the Holy Grail. When quaffed from, something good happens; perhaps it needs to have charges or invoking it fills it up so you can drink from it (and you don’t have to drink from it immediately, allowing strategic choices). Should give magic resistance when carried. Possibly gives the effect of a random potion when quaffed: always a “good” potion when blessed, a random one if uncursed, and a “bad” potion if cursed. Or it blesses items dipped into it.