The Curse of Strahd
This silver War hammer had slain countless fiends and undead from when it was forged for Knight captain Wojak to when it was interned in his tomb after his fall. The hammer had been inscribed with dwarven runes, intertwined and inscribed in unique ways lost to the ages which granted it singular abilities. Yet the secrets for activating these abilities seem to have been lost when the order of Argynvost fell.
Magical analysis showed it to have a rudimentary magical aura of strength on its surface, but it seemed there was something stronger under that aura, yet their was no way to know what it was.