Lich's Bane

The Lich's Bane is an ancient bronze blade, dating at least as far back as the late Asurian Empire. It is said to have already been a powerful magical weapon, though its abilities in combat have long since been lost to time. It was last used in the legendary battle against Kalshazzak Aesymnetes, the emperor who dared to seek apotheosis by sacrificing his own empire. While that battle was hard won, it came at no small cost. Kalshazzak achieved a form of immortality, though, through a divine miracle, he is cursed to bear the form of an undead lich for all eternity, forever denied true deification. However, no immortal can ever truly be slain, so after his defeat, the gods and the mortal heroes who gathered to defeat him devised a seal, such that, to the dying days of Eshor, he would never again walk free. This binding called for the use of several powerful artifacts, their great enchantments giving them the integrity to survive the power of the seal coursing through them. These sealing artifacts were laid out, tracing a mystical rune across the landscape around Caelester, the lich's final resting place. Knowledge of these artifacts is hidden away in secret tomes kept by a handful of religious orders, preserved in secret by their most trusted scribes. Their locations have been lost to time, with only scattered clues in the old tomes hinting at their possible locations - all save for one: the Lich's Bane.
This ancient bronze blade is the centrepiece of a secret shrine, deep in the basement of the Abbey of Caelester. Here, the Abbot of the Order of the Divine Wills, along with a handful of the most trusted monks of the order, prays over the blade, monitoring the integrity of the seal and renewing its power, in hopes of preserving its power forever.
Despite their best efforts, the seal slowly weakens. So slowly, in fact, that nobody realizes just how close it has come to the breaking point.