An aboleth written out of the story
Yiggnaroth is a powerful ancient Aboleth. He lurked below the swampy murk that used to be Weissland and ruled over all sentient life in his watery domain. The three founders of Weissland vanquished him and established their royal houses in his former territory after they had used arcane magic to dry up a great deal of the swamps. However the three did not realize that Yiggnaroth yet lived. He survived in a state of suspended animation after he had drifted to the seemingly unreachable bottom of the watery catacombs below what is now the Wraithwall Sluices. From there his dark and twisted dreams found their way back to the surface and those that heard them began to fall under Yiggnaroth’s control.
These unfortunate souls began to do his bidding and were eventually drawn to his resting place. There they formed a cult devoted to the aquatic monstrosity and attempted to undermine the control of the descendants of the three houses over Weissland. The cult was known as The Fourth Family. After a series of setbacks, Yiggnaroth reawakened fully and began to direct his minions consciously. He created a strange parasitic slug that allowed him to control victims that were infested by the slugs. He ordered his minions to covertly begin infecting the populace of Weissland.
Cecilia Rainsworth discovered the slugs and went about making herself and her servants immune to them before they could be targeted. The slugs required a living host and could do nothing to undead. Cecilia and her most trusted servants are currently the only ones who know Yiggnaroth is still alive and are actively trying to kill him. Unfortunately for them Yiggnaroth’s lair is technically in running water so Cecilia can’t get at him with any of her servants that are powerful enough to battle him.
Of course none of the other characters in the story knew anything about him, so, game master Sherry wrote him out of the story.