How many adventurers’ last thoughts were “strange, this tunnel seems cleaner than most?” Too many, and all because of this transparent menace. A great acidic blob that expands to fill a small chamber or corridor and then slides, ever so slowly along, eating everything in its path. It cannot eat stone or metal and will often have them floating in its jelly mass. Blech. Instinct: to Dissolve

• Occupy unexpected spaces
• So transparent you can just walk in unknowingly
• Make a special action related to its random element
• Roll over on them