Just some observations (in the order of voting entry appearance)…
RayVelcoro: Such nice textures and volumetrics in this one!
3dnotguru: That footprint looks fairly fresh, and with a hint of shadow just off to the right, perhaps the Yeti is nearby…
Fulip: Such an energetic glowing effect, something which reminds me of some of the bioluminescent vegetation of Pandora in the movie Avatar.
Evilos: There is some seriously supernatural stuff going on here, perhaps something out of Dr. Strange’s universe…
str11: Ahh, more bioluminescence is a good thing! It’s amazing to me how naturally some things in our world can produce their own illumination.
purbosky: That plant must be really hungry to want to swallow the moon! I wonder what it had for breakfast…
Phantascene: The first thing I thought of when I saw this was the scene where C-3PO and R2-D2 were riding in the Jawas’ Sandcrawler. The movie AI also comes to mind. Poor droids!
fcharr: This looks great, like something right out of a commercial-quality game. I read and admire how you achieved the lettering outlining. Great work!
mik.a.: Great idea and nicely realized in a hauntingly cool way!
YAFU: I admire how you stood with this piece and developed it further. This image really captures the sense of the supernatural.
Unicornaphobist: I really like how you went with a distinctly different interpretation of the topic.
appie.123: You have “unleashed the Kraken” well here! The details on the tentacles and sea floor are especially nice.
david.speer: Several things here – the eerie tree outside, the books coming off the shelf, and the green glow – all contribute to the successful supernatural nature of this piece.
Enthymeme: This is yet another great alternative take on the topic, and the artistic and technical details contained in this piece (which really emerge in wonderful ways thanks to the video you also provided in the entry thread) are really admirable.
SonnySee: I love the idea and appreciate the way you used various tools and techniques to develop your image.
DoriNori: A very ghostly image full of the sense of supernatural! The Pac-Man ghost in the background and what appear to me to be dots along the wall on the left make me wonder if this could be “Pac-Man’s Basement” 
caz747: Another nice example of using multiple tools to achieve the image you had in mind! The wave modifier on the water works perfectly here. The water is also convincing. Back in 2005, I tried my hand at visualizing the Lady of the Lake, and it was fun. Your sword is far more realistic than what I made back then 
Helge: Such a happy creature! His horn could also double up as a party hat =) The colors in this piece really help to support the undeniable cuteness here! Also loved your “supernatural bump.”
Photox: Excellent work, as usual, and the face between the trees really helps underscore the hauntingly supernatural presence in this scene. I also admire the very artistic approach to this image!
LeoBlenderToon: Very nice use of toon shading and lines in this piece! Compositionally, this is also very nicely arranged (both in terms of “the rule of thirds” and nearly the “golden ratio”). Very effective!
TenRado: This is yet another nice example of taking a imaginative and compelling approach to the challenge topic!
RobertT