Within the secret door, you find a stash of occult items. Of immediate interest is a bloodstained tome, open to a page that shows an amalgam to the ritual sacrifice just performed. Cyrind'ae (and perhaps others) is able to read the mystical writing, and discern that the portal will remain open for an hour, but can be closed early by a standard counterspell (like Dispel Magic), or by damaging it with radiant magic. Fritz is able to accomplish this with Sacred Flame, and the portal does indeed close.
The wizard that you subdued and killed is apparently Nilas Hornwick, a name that will mean little to any of you. You discover, by subduing the remainder of the cultists on the upper floor, that Nilas is the brains behind this adventure. With his death, his true plans remain obfuscated.
Nar is able to rededicate Grok's prehistoric blade, and he wears it proudly now that he knows it is become a force for good. In time, you all notice that which he had realized - the dagger's influence has increased his capacity for reason, perhaps even up to human average, if such a thing could be measured by a simple statistic.
Helge returns, haggard and worn, from her battle with the dracolich. She seems to have been aged by the ordeal, and immediately falls asleep in her home. Old Man Sydell thanks you on her behalf, and by his tone, you understand that he would spend her few remaining hours alone with his wife.
Your service to Marian Town, and to the Duchy of Harcourt, is rewarded once more, with feasting and accolades. The Duke attends Helge's funeral, extols her magnificent contributions to the defense of the land, and presents each of you with further recognition and rewards. Sometimes, only the bravest and most competent of heroes are all that stand behind civilisation and the forces of chaos and destruction.
You are certain, however, that the Duchy of Harcourt has not heard the last from Orcus, the Prince of the Undead.
Here lies the end of our adventure. I would like to thank all of you for bringing your characters so richly alive for the rest of us.