Witch's Jelly
This dangerous anomaly can be found in low places such as ditches, sub basements, sewers etc. The main threat of this anomaly is that it is nigh invisible to the naked eye in daylight, but it gives a soft bluish glow in the dark akin to a burning alcohol stove. Due to this, many a waster has jumped into this hellish anomaly without realizing it was there and lost either life or limb. Upon contact with any living creature, the Jelly reacts with the molecular structure of the organism's bones turning them into a thin rubbery like substance. Anything unfortunate to have dunked a limb into this nightmare will quickly find the limb to be practically boneless, painfully flopping or giving way to any weight placed upon it. Woe betide the poor bastard diving into a ditch for cover only to realize that it was home to a Witch's Jelly.