In one world of normal people in the Republic of Normalicia, the Hosts of Heaven and the Forces of Evil dueled. Heaven won, and shut the doors to the dimension next door, but because of certain dimensional physics limits, was only able to fully close the doors the vast majority of the year.
Next door--dimensionally speaking is the Land of Things We Don't Like. Its full of creepies and ghoulies.
On All Hallows Eve the great doors between the dimensions start to open. Cemeteries, dark alleys, and empty hallways become places where you can cross over. So they are avoided. But this opening also creates a great sucking of dimensional forces. Things that are not tied very strongly to their home dimension tend to find themselves shifted.
Things like children who wish themselves far away from their horrid home, and gating wizards, and versers. Lots of versers. Typically over twenty versers arrive on this dimension yearly.
Once Halloween begins at dawn on Octomber the 30th, the gates are fully open, and the suction is gone. The creatures of the night begin to infiltrate Normalicia. And its actually pretty safe unless you find a monster's hiding space (closets are popular), (and thus the parental threat--'eat your spinach or I'll make you clean out the closet' has special force this day. Much spinach is eaten.
Some monsters actually do have power in the daytime, but most wait for nightfall. And of the ones that do have power in the day, most are like goblins, and not as powerful.
Once night falls, and its full-on monsters.
However, the people are not unprepared. They live in denial, but one of the favorite candies is garlic caramel handed out to each trick or treater. Pumpkins carved are a protective force against the Headless Horseman. No one goes alone for fear of the Wild Hunt. Some extremely scary and technologically effective 'fake' ghosts scare off real ghosts (ghosts have a hierarchy, and yield to their superior in hunting privileges).
However these only work to some degree. And any hardpoints that people try to create are destroyed by the forces of evil. The Great Commanders of the Dark know that if enough human hardpoints are created, enough churches singing Christmas carols, enough Mage Towers with layers of spirit wire and shadow machine guns emplaced about them that the humans can beat them off. So the Great Commanders desperately attack any hardpoint to destroy it to send a message. Some few of the Light have begun forcing the evil to attack hardpoints which are manned with the near-dead. This causes the Dark to waste much of its strength to attack a few. But this counter-strategy is very new, and some think its evil.
One way to be safer is to be the only believer in Halloween on a street of non-believers. Its like having the only locked car on a street of unlocked cars. Sure the thief can probably break in, but why should he bother since all the others are easier.
A number of the magics that fend off monsters can't stop them. They just require the monster to take several successful Difficult willpower checks to get close, and then he's ok.
Most of the monsters operate in the cities where there is a larger herd. But even in the Back Country of Alaska there is at least one monster in the area. Frequently country folk get acquainted with the ways of 'Their' Monster. In the city and suburbs, its more anonymous.
At dawn on All Saint's Day (Nov. 1st) the doors begin to rapidly close. Within a few hours everyone that has come is blown back into the holes they left in other worlds. It is possible to resist the push with a Simple check. Some people get blown back the to the world they came from the next year. Oftentimes the receiving world has a Gabby's Gate which states 're-entering dimensionals must appear to be as they left physically'.
Thus you have cases of children wandering into their room in sadness, and getting sucked into Normalicia for a year, and then getting blown back, and looking the same as when they went in the door, but they are a year older, and probably wiser and they understand more since the folk of Normalicia are pretty nice.
And on All Saints' Day, there is a big street party. No one says the purpose, but its to find out who is still alive among your friends, and reassure everyone else, and connect. Its a highlight of the year, competing with Christmas for top honors. Its the Festival on All Saints' Day. But few versers see it as they are blown back to the worlds they came from.
And thats a concept called a Temporary Gather with pseudo-scientific justification included.
Note: This world would be a lot easier to make if there was a "Multiverser Monster Manual".
Eric
