So im new on the forum and noticed the monster contest, that is long over so oh well, still had an idea i thought i'd put out there even though it may be taken. This is a 'monster' that can appear on literally any planet, its origin is unknown, and its made up natural terrain like a golem or elemental might be. They can be trees, dirt, rocks, mud, lava, almost any block. They are undetectable until touched, either by walking on them as they are grass, or attempting to mine one. You might be digging underground and find a vein of a nice mineral you need, thats all it will look like. You'll try to mine it, and there will be sound, and blood, and you will know you done bad. The material will come to life and break free of immediate surrounding confining blocks to attack you, mining weapons will work against these monsters who need broken to pieces until they stop moving. They'll reward you with the material they are made of, naturally. They are basically Mimics but in the form of material instead of chests, and the name is derived from Terror + Terrain. I think they'd be a genuiningly scary monster since they are completely unpredictable and more lethal based on the rarity of the material they are composed of. The names kind of a mouthful, need a better one, like Terrabio?