This is my submission for Group Build XXVI, and you can follow my whole adventure of making this here:
http://www.miniwargaming.com/forum/viewtopic.php?f=113&t=62152&st=0&sk=t&sd=a

This piece is full of symbolizations and meaning and stuff. Here's a copy of what my thoughts were when planning this:

"Okay, so ever since the topic was announced, I've been trying to think of the most evil thing that would be appropriate for this build. I really wanted to make a statement about deeper evils inherent in human nature and not just the more obvious evils of demons and things, so this was a bit tricky. I played with the idea of having a human temple with witches being burned at the stake, and I also thought about trying to show an interior shot of an industrial center where hive-planet workers rotted where they died in exhaustion amidst the gears and pipe-works of the uncaring Empire of Man. A symbol of religious intolerance, and a symbol of lack of compassion, either one brought to the extreme are quite evil in my book. Unfortunately, I am once again on a budget of $0, so what I'm making has to be built with materials I've already got. Both of those examples would require me to buy more minis for "background" purposes. Instead, I've opted for a more "environmental" terrain.

A park; being advanced upon by a river of sludge, out of which emerges a decaying demon which reaches forth to claim the life of the last living tree. Everything the demon touches dies. Black tar-like goo drips from its mouth and eyes, and the decayed skin is tightly wrapping the bones where it is there are all.

My original inspiration for the demon was Hexus from the movie Fern Gully, and I thought about having this thing as part of a ritual to Nurgle (maybe like it was emerging from the warp onto a feral planet or something) but I decided that I'd rather have it left open to interpretation so that it might be usable in things other than 40k since I want to sell it when I'm done. I do intend to have some barrels of toxic waste and maybe some industrial runoff pipes leading to it with bits of trash and discarded things as a further indication that Man was the cause of the problem.

The complete destruction and utter disregard for the welfare of the natural world. That's about as evil as I can think of for building something in the budget I'm in."

-xand