Two things that lean on our Fort's purpose were reinforced with this quest. The Zamorakians outside of the north gate are certainly as active as we are as tensions rise, and the mysterious "Z" who convinced Bianca to infiltrate our fortress probably does have a bit of a personal history with the area around Varrock.
My theory, is that this particular questline has a whole lot to do with a Mahjarrat that was just put in his place by a human-hybrid and thwarted in the area a couple of times now. His name is Zemouregal, and this time it won't be an alternate reality where we finally put the fiend down. His time is running short....Maybe - we'll get there.
Rationale for this. Three points.
> The Misthalinian royalty is Zemouregal's traditional enemy.
> Zemouregal starts with "Z".
> If there's one thing Zemouregal is an expert at, it's a little something called "necromancy"... and I can't imagine why that would be important. If we don't somehow extract his secrets before finally ending his life, well... He will die, regardless.