This creature looks like a man-sized rotting tree trunk with several thorny tendrils sprouting from its body. A single limb protrudes from its central form as well.
Str 18, Dex 10, Con 20, Int 3, Wis 14, Cha 6
Three times per day, a bog creeper can spew digestive acid from its mouth in a 30–foot cone that deals 2d8 points of acid damage to all creatures in the area, with a DC 20 Reflex save allowed for half damage. The save DC is Constitution-based.
Since a bog creeper looks like a plant when at rest, it takes a DC 20 Perception check to notice it before it attacks. Anyone with ranks in Survival or Knowledge (nature) can use one of those skills instead of Perception to notice the plant.
A bog creeper can move across marshy terrain without incurring any movement penalties.