The Nether is the creepiest place in Minecraft--essentially it's the game's version of hell. This seed initially takes you to a peaceful plain setting with a very short walk to a village. The village itself is standard fare, but in it, you'll find a portal to the Nether.
There are the usual things to be found there, but the user also created a Nether Fortress to tackle, with the accompanying chance of finding Zombie Pigmen and Skeletons, among others, that you'd expect from a Nether Fortress. If you're in the mood for a helluva good time this Halloween (sorry), this is a great way to do it.
Like you'd expect from Minecraft, thee possibilities for creating your ideal Halloween scenario are almost endless, whether you like survival or zombies, dungeons or temples.
Let us know in the comments which seed you'll be trying out or if you've got a Halloween seed to share yourself!