No real plot I'm afraid, just a bit of world building to be getting on with while I work out what's going to happen in the next proper chapter (by the by, if anyone has any ideas or suggestions regarding events or characters, feel free to share).
Disclaimer: As always, only the words are mine.
Although the countries that celebrated Halloween were few in number, the chaos magic spread far beyond them so that there wasn't a single inch of the planet that was untouched, or a single person that wasn't affected in some way, either directly or indirectly. Even the most isolated of societies and tribes felt the impact, as they watched the sky turn red and found that the beings of their legends and beliefs became all too real, along with the creatures that were created from the psyches of the outside world. There was no escaping from a world gone completely mad, no matter where you hid or how far you ran.
As humanity struggled to survive in the aftermath of the Halloween chaos what they didn't realise was that in some ways they'd already lost the battle. Approximately 20 of the world's population was wiped out in the first month, although this estimate changed on an almost daily basis, going down with every new pocket of survivors that was found and back up again with every report of a town or city reduced to rubble.
Of those that had survived, over 50 was in some way altered, ranging from full transformations with the original personality completely erased, to people who's personality survived intact but found themselves in different bodies, to those who remained much as they once where with the exception of the addition of a few traits brought about by proximity or kinship with those more affected. Out of the transformed, an unknown but significant percentage, possibly even the majority, was either non-humans, hybrids, or some form of subspecies. While a sizable number of 'pure' humans continued to exist in the post Halloween world, the number continued to be reduced due to attacks, food shortages in the more remote areas and periodic disease outbreaks due to poor sanitation in overcrowded shelters that lacked the resources of the more successful colonies. There was also the fact that out of those who were unaffected, the majority were middle-aged or older, while the younger generation had for the most part been altered in some way. In the everyday chaos of surviving no one stopped to think about this or considered that what they saw around them was repeated the world over. Perhaps it was best that they didn't, because if they did then a single stark truth would have become apparent. Even if they managed to survive the monsters, 'natural' disasters and general upheaval, humanity's, (or rather the pre-Halloween concept of it) days were numbered.
Given the ratios of transformed to non-transformed, (not to mention that people are shallow and it just so happened that the ranks of the transformed ran high
to hotties), hybridization was inevitable and given the semi-isolated nature of the colonies, it was only a matter of time before the vast majority of the world's population had something other then bog standard human somewhere in their family tree. There had already been a certain amount of crossbreeding going on between humans and various compatible species prior to Halloween but that had been the exception rather then the rule. With the sudden explosion in both the number and variety of non-humans, the majority of which were outwardly indistinguishable from humans and perfectly capable of breeding with them, this would change sooner rather then later.
How much of an issue the changes to the gene pool would be depended entirely on your outlook. If you considered humanity to be defined entirely by culture and genetics then it would be a disaster, nothing short of extinction. But if you defined it by something that was simultaneously more abstract and more fundamental then it wasn't quite as bad. The new human race, or races, might differ from their ancestors in terms of DNA but they'd still have families and friends, still fall in love and fall out again, still talk and joke, argue and fight, still work and play and laze around on days off. People would still be people, even if they weren't what everyone would consider to be entirely human. Whether humanity and its many and varied offshoots would survive long enough for this to happen was another question altogether, one which only time would be able to answer.