I managed to find all 22 Collectible Minifigures at my local Target in Minnesota. I think it's worth noting to others that are hunting that these were hidden away at the front of the store a 4 registers next to all the candy and gum and such. I never would have found them if I hadn't asked!
I was almost starting to doubt the existence of the devil's snare on the D2C Hogwarts, but there's a picture on Instagram of all the parts of the castle dumped in a pile, and you can clearly make out two vine pieces (Bionicle appendage in dark green) - one in the middle and one on the left, so it definitely exists!
Also, is the snake mold in silver in the Chamber of Secrets, the 4 statues on the side, that is, a new mold? I find this an odd choice as there aren't many new molds in this set. I know a Chamber of Secrets isn't likely at this point, but I'm guessing LEGO intends to use that snake mold for something. Or maybe it's old and I don't know what I'm talking about.