From publisher blurb:
In Red-Eyed Phylactery, the king summons the characters to help solve the gradually fiercer attacks of an undead magician who emerges from the sewers and attacks all around him. Despite the abomination being destroyed three times already, it keeps coming back, each time stronger and more cunning. The characters must track the lich back to its lair before its body reforms again and he attacks the kingdom's capital once more.
This Shadowdark adventure brings the heroes to an undiscovered crypt under the city. It has been there without being disturbed for over 5 decades. Within, the characters learn of the nature of their enemy, an immortal spellcasting lich. To defeat it, a mysterious magical vessel known as a phylactery must be found and destroyed. The vessel is in the dungeon but a wall of force protects it. The characters must find a way to disable it or else the lich shall appear before them.