Eirmont 5 is Necromantia, the national holiday of Klantyre. "The people go to the graves of their ancestors to pay homage and to clean weeds and dirt from the burial sites...[o]n the night that follows this event, ghosts and spirits are rumored to visit their descendants. If proper respect was shown, then nothing is to be feared; but some disrespectful families have been found dead the next morning, with expressions of utter fear on their faces."
Given the McGregor origins and the visitations of dead ancestors, Necromantia might be a time when the barrier between Laterre & Mystara is weaker too, as well as the one between Mystara & Limbo.
Here's an adaptation of my town of Samhain to Mystara:
Necromantia
by RipvanwormerNecromantia is a town with four gates. To the north is the gate to Mystara. To the east is the gate to Annwn, land of the deep sidhe. To the west is the gate to Svarthalfheim, land of the dark elves. To the south is the gate to Limbo, the realm of the dead.
It is difficult to say for certain where in the multiverse Necromantia lies. Some say it is located in the roots of Yggdrasil, the World Ash. Others say it's located somewhere on the plane of Thorne, while still others think it's an outer plane in its own right.
Once a year, on Eirmont 5, the gates open. The dark elves and sidhe come in. The souls of the dead come in. And the gate opens to the mortal world, and on this one night the fey and the unquiet dead can mingle among the living and no Immortal can stop them.
The rest of the year, Necromantia is a purgatory of sorts in which those who for whatever reason find no welcome among their kin in Annwn or Svartalfheim live among those unquiet souls who have managed to temporarily escape the wardens of the dead. There are also a few mortal witches and shamans strong enough to live in Necromantia without being stolen away by one faction or the other.
No one knows who created the gates. They look like crude archways made of massive stones. The locals call the builders the Old Ones and believe when they set the gates in place they also set in place laws that no spirit, fairy, or Immortal can disobey.
Besides the four main gates of Necromantia there is a fifth gate that leads up a narrow, winding path carved into the roots of the World Ash Yggdrasil. At the end of the path is Good Sprite, a small town in the plane of the fey. When a fairy dies—be they sprite, pixie, sidhe, pooka, or other—and returns to life, first their shade passes through the Limbo Gate to Necromantia where they must reside in the town until the gate to Good Sprite opens on Nuwmont 1. Only then can they walk the narrow path up the World Ash and emerge in the light, reborn as a new type of fairy.
The mayor of Necromantia is Jack, a tall, skeletal figure in a fine white suit. He rules uneasily, striving to keep a balance between the ghouls, boggarts, witches, ghosts, goblins, necromancers, dark elves, and scarecrows who make up the town's population.