Very nice animation!
Dang, dude, I really got into this. You really captured the spirit of horror with this. Like the girl who gets snatched up in between frames, almost. That was grizzly. Not a word was spoken, and so much eerie information was communicated. Alright, I gotta break this down, my experience.
First you have the girls (great art style, by the way, keep THAT up, seriously) who wonder off on an innocent Halloween's night, every parent's nightmare. They come across an abandon house. Why is it abandon, the viewer asks? Well, because it's where HELL finally leaked through, and is eating up the area around it's origin point! As we quickly learn in the next few seconds.
Then with the music getting deeper, the first girl gets separated and within a heartbeat, gets taken like a spider gobbling up a fly. While the music continues, and as the views starts dreading, in thought, about what kind of horrible things are happening to that last girl, the next girl gets separated and we sink in our chairs in loosing all hope for her when we see these fingers pull the ground from beneath her feet.
Falling, I think is an underrated fear, it's so terrible to think about. Think about how our bodies fear it so much, that, when we're falling asleep, we often have night terrors where we think we're falling out of our beds. And during that millisecond that we think we're falling, there's so much terror going through your brain when its an unprepared fall, that it literally feels like we're being electrocuted. That's just a millisecond! Imagine going through that for the entire time it takes for you fall through stairs.
Then to take it to the next level, we see the very last thing that she sees, an image that her mind will no doubt cling to for an eternity; always reaching for the light, but not quite getting there. Wicked spooky.
The last girl, I almost got lost at, because I had to wonder why she was even still around, being that she was alone (A childlike superstition that says we can't be harmed if we stay in a group, well, better than a superstition, it actually goes back very primitively, but I won't get into that right now) But then she turns out to be the monster, and the horror turns into comedy, as the t-rex reference ensues.
So that part, I gotta give you kudos, not only was it a bit of irony, you chose to bring us, the viewer, out of all these DARK thoughts and put a happy face on it, pulling us back into 'the light'.
Yeah, all in all, I think this was a WONDERFUL Halloween story. Don't lose that writing ability, bro.