Adrianna Whitestar - Paladin of Tyr.
The group, the Crypt Walkers, was tracking down a murderer who was concentrating on women. We'd had several close calls with trying to catch him, and Adrianna and one other character were even attacked during particularly bad night of fog (they couldn't see their attacker, and Adrianna was slashed across the back of the hand before the attacker withdrew). Doing some research, it was discovered that a knife which was brought back from a previous Ravenloft adventure (just before Adrianna joined them), and subsequently misplaced by a party member, was possibly responsible for this... a cursed knife which was forcing someone to wield it as a murderer. In our research it was found that the knife could be stopped if it was either held by a (person of) pure heart, or held within a pure heart (the translation of the text wasn't clear on this). Of course, everyone looked at Adrianna at this point.
On our next encounter with the knife wielder, it was going after a local merchant lord (who was, as it turned out, also a priest of Loviatar) and Adrianna found herself in a corridor with the knife-wielder and the merchant lord, and attacked the assailant slashing at the user's hand to spare his life. Although her strike was true, her blade contacted steel instead of flesh and it was discovered that the knife was, in fact, wielding itself, and projecting an illusion of a cloaked person using it.
Adrianna dropped her sword and grabbed the knife out of mid-air, causing the illusion to vanish. Struggling with it as it attempted to make her slash her own throat, she was forced deduce that the text they translated did not mean for it to be wielded by a person of pure heart.
In that moment, she made the choice to end the evil of this thing and stabbed the knife deep into her own heart. As she died, the priest revealed his true identity to her, and when her friends arrived, they only found her sword and a large pool of heart's blood on the floor. The cleric had taken her body with him, so that he could enact a ritual to extract the knife and control it.
It took months for the group to finally find the hidden lair of the priest, where they discovered him attempting the ritual. However, before he could remove the knife, Adrianna's spirit returned to her body, grabbing the priest's hand and keeping the knife were it was. The group was able to attack and defeat him, and he, along with Adrianna and the knife, were swept into his Sphere of Annihilation, never to be seen again.