Through some celestial mishap or accounting error, for some reason, Hoobynoob falls on Freday the 13th of Octember, in this, the 47th year of the Subsidence. Normally, of course, Hoobynoob falls on the 30th, the last day of Octember. The 13th of Octember doesn't normally even fall on a Freday -- it is typically a Munday.
This calendrical irregularity is known for certain: all the experts agree on this unusual occurrence -- the astrologers; the astronomers; the druids and rangers of Sequoia (who counts the months and weeks, the planets and stars, under her purview); the calendricians and calendrometers; we even asked the janitor, as they know of these things.
Amongst the populace, once the confusion is overcome -- or at least set aside -- the yearly observance of Hoobynoob proceeds as usual, albeit on the 13th. In Endeesy, capital of Gus: gourds are carved; nuts are harvested; costumes are prepared; candies and sweets are purchased or crafted in bulk in preparation for the traditional mass extortion, on threat of prankery, by children.
When the 13th of Octember arrives -- on a Freday, just as (unusually) ordained -- the morning sneaks into Endeesy foggily. The day slugs by: children growing increasingly excited, adults growing increasingly wary of danger, the weather growing increasingly foggy and moist-smelling.
When treat-or-tricking time arrives, it is nigh impossible to find one's way in the fog. But, through some divine Dalyan providence, unusually alert priests of Dalya, and widespread use of the Buddy System, no children are separated from their guardians for long.
The children return to their homes, feast on junk food, and repair engorgedly to their beds. After the foggy day and foggier evening, it looks like it has been another successful Hoobynoob, profitable for the children and fun for all ages! Parents go to bed. Bar crawlers begin the process of acquiring their holiday drunkenness.
Midnight approaches.
The clock tower in the Cathedral of Quasxthe in the Crown District of Endeesy ticks over from 11:59, and the mighty bell begins its twelvefold tolling: BO-o-...
The bell, having tolled half of once, trails off, as if it has forgotten how to bell.
Mournful moans are heard through the increasingly farty-smelling fog.
Zombies! Some of whom are fresh, some of whom are decaying and dirt-encrusted.
Following the trail of zombies leads the party north, to a graveyard in the Resentment Ward. The zombies are discovered to be animated by worms squirming under their skin (a miniboss zombie acts as Spawn of Kyuss).
A 400-year-old mausoleum, dating to the early centuries of the Inundation, proves to be the resting place of the Mermaid Queen Riefya I Arielid "the Black".
A party member recollects a fact about Riefya "the Black": that she was found, after her death, to have secretly been a cultist of Asya, goddess of all that is disgusting.
The lock on the door, being 400 years old and having been underwater most of that time, has become more of a jam. But somebody has already broken the jam. But somebody subsequently cast an arcane lock on the door. But the rogue breaks the arcane lock.
Within the tomb, reality is distorted. The air is fetid and moist. The stairs down are greasy. The walls are fleshy and moist. It is not a throat, but it desperately wants to be a throat.
At the bottom of the stairs, the tomb of Riefya has expanded from a small room to a large acid-lake cavern, as if it wants to be a stomach.
A sarcophagus stands on a raised dais in the middle of the acid lake. A mage stands by the sarcophagus, incanting a ritual.
He is Vyndoc Hogkt, a descendant of the Hogkt family that ruled the Asya-worshipping Plaguelord nation while it existed in the first century before the Inundation. (He is a Mage, with spells swapped out for poison- and acid-related spells.)
His ritual concludes, and an oozely incarnation of Asya possessing the corpse of Queen Riefya joins combat. (She uses the stat of a Black Pudding, except she can throw acid gobbets -- her Pseudopod has a 60' range.)
Time progresses from midnight once they emerge from the tomb.
Hoobynoob did not come on Freday the 13th because of Vyndoc (that's an unsolved mystery), but since it did, and both 13 and Hoobynoob are sacred to Asya, he took it as auspicious to enact his plan.
