Blackstone Campaign: The Cult That Waits

One of the overarching plots in my AD&D 2e S&P campaign (which is 13 years old already) is about M'Andry V'Heve've, a term in an ancient, almost forgotten language, that means She Who Waits.

Spoilers Follow: My Players Stop Here

Now for some secret history the players only have brief glimpses of.

The Time Before- Since the Jade Empire 9in the Neolithic!) the First Lich, She Who Waits (M'Hendry V'Varhe'he), has been sealed in her prison, bound about by nine seals that forbid her to leave. The perpetually Undead High Priestess of the Ghoul God, her powerful followers can enter her prison and speak with her.
  For millennia she has watched human empire grow and used her cult to corrupt the powerful into worshipping her foul master. She carefully shepherds a few necromancers into having the combination of knowledge, power, and devotion to break a seal or three then destroys the empire before anyone is powerful enough to destroy her (and the mass death of the violent collapse pleases her evil master).
  Her cult brought down the Jade Empire (although she was sealed away as it fell), the Ruby Empire, and the Emerald Empire. By the time the campaign started she was bound by only 1 seal and had a follower with enough power to break it!
  Luckily this man had been killed and cremated. Very unluckily this man, called the Broken Man, had received a dark blessing from the Ghoul God - if his ashes were gathered together he would regenerate and live again. Even scattering them to the wind or waves would not stop this, so his ashes were gathered into 5 lead jars, scattered, and hidden.
  A recurring arc has been to keep the five jars of the Broken Man's ashes from being gathered together.
Through all these long years the Cult That Waits, evil necromancers and ghoul god cultists, have worked for She Who Waits as her eyes and ears

  During the 13 years of the campaign the players have fought the Cult here and there, over and over, but about 80% of the time they didn't know it. The wererat thieves of Blackstone? ultimately controlled by a ghoul god priest. The venal and corrupt Lord of Burgen? Paid by the Cult to leave the northwest border weak. The attempt to resurrect the evil Champion of Wasson? Paid for by the Cult. etc.

Her Problem-   With the Gate to the Negative Material Plane sealed She Who Waits is rapidly approaching demi-lich status (a fate she has avoided for eons) meaning that for the first time since before the dwarves learned how to make bronze she has a lime limit. In 5 games years she will begin falling into the twilight sleep of the demi-lich.
  But the Cult is really running out of leaders! Last weekend the PCs tracked down Lord Joras (the most powerful surviving Necromancer) in his mountain fortress, fought their way through 80 zombies, 12 ghouls, and a ghast led by a Juju Zombie archer as well as the shadows and wights Joras Summoned and even Joras' own spells (he taught Creepyhead the trick of combining Spectral Hand with Clairvoyance and touch attack spells).
  Although sealed away behind a powerful ward with the entrances to her prison sealed under thousands of tons of rock she is, for once, desperate.
  Now the surviving cultists must flock to her island prison and dig her out while the most powerful of them desperately try to get the jars of the Broken Man back. Why?
  There is another Gate to the Negative Material Plane open, in the lake of Veridian, the accursed former capitol of the Emerald Empire. If they can dig her out and break the seal She Who Waits might avoid demi-lichdom another 20,000 years....

What's Next for the PCs- Reports of attacks on the Holy City and even their fortresses as the last of the cultists scramble for the jars and reports from their agents and contacts that hundreds of people are travelling to the most remote area of ocean in the world.