Evolutionary happenstance has created a clever underground predator. Disguised as a rocky formation—most often a stalactite or stalagmite—the roper waits for its prey to wander by. When it does, whether it’s a rat, a goblin or a foolhardy adventurer, a mass of thin, whipping tentacles erupts from the thing’s hide. A hundred lashes in the blink of an eye and the stunned prey is being dragged into the roper’s mouth. Surprisingly effective for a thing that looks like a rock. Instinct: To ambush

• Ensnare the unsuspecting
• Disarm a foe
• Chew on someone