Halloween is no Christian holiday, no matter how the Christian fathers have tried to spin it and roll it and make it that way. All Hallow's Eve and All Saints Day just don't cover the vestiges of the old pagan religion.
First, Halloween is Samhain. You pronounce it "sha-mane" and it one of the major festivals of the old Celts whose modern descendants include people like me, today's Irish, the Scots, the Welsh, a few Brits, some French and, I am told, a National Basketball team in Boston which does not know how to pronounce Celtics.
Samhain was celebrated by the Druids, One of the Druids, I am told, was an ancestor. It is not a particular matter of pride or shame. Having a Druid as an ancestor might even be a plus factor when it comes to Samhain.
Samhain began (as the secular Halloween does) at sundown of Oct. 31. It ended at sundown on Nov. 1. Celts, like the ancient Jews counted days like that.
While Samhain was in progress, it was either fun, or horrid, depending on whether you really got along with the dead.
Samhain is dangerous which does not mean it is particularly bad. It simply means Samhain is dangerous.
Essentially this is what we are talking about here
After dusk falls andthe winds begins to freshen and the moon hides behind the clouds, the barriers between this world and the Otherworld and the Underworld began to shimmy and shake and blind in particularly stressful way. Everything goes wrong in space and time. Humans and other things, some too unspeakable to name and some which smell bad, begin to wander into realities where they would no wander on any other night (or day).
You can't miss Badbh.
She's the one in a long black dress with flashing blue eyes who does not need a flashlight to get around in the dark. She is the one who moves in the trees and through the towns on a wisp of winds. She is the one who is a lot worse than Donn, whose only real danger is that he doesn't like walking around in this world anymore than the other residents of the underworld. Donn and his minions will panic a little if this world gets too stressful and might run over someone trying to get back to Annwn. But they will not mess with Badbh.
She appears in threes.
She will be hideous
She might be dressed in black or naked. If naked, she will be bleeding.
Black is the color of death.
And on Samhain in the olden times, the ancient Celts were accused of human sacrifice on this night to counter the terror of the wandering spirits and the Badbh. Nobody ever proved it though. We Druids don't sacrifice people. Only politicians do that.
All Sabbats * Yule