Gargantuan Praying Mantis

Picture an ordinary praying mantis enlarged to monstrous scale. Its soft, nearly translucent green coloring blends with its surroundings well enough to hide it 45% of the time. Its huge forelegs are lined with thick bristles that make its grip hard to break: a captive must pass a Dexterity check at -1 for every two Hit Dice the mantis has. Its hard exoskeleton starts at AC 5 and improves by one point for every two Hit Dice beyond two, reaching AC 0 at 12 Hit Dice.

It waits for prey to come to it, then pounces with total surprise. The spiny forelegs seize the target, dealing the first two listed damage amounts, and the bite delivers the third; damage depends on the mantis's size. Morale never enters into it: the mantis fights on until its wounds total half its starting hit points, then abandons the fight on the spot to look for an easier meal, even when the prey is moments from death.

Each mantis hunts alone and defends its range savagely against its own kind. They never team up on big prey, and one will even set down a fresh catch to drive off a trespassing rival. The only peaceful meetings are for mating, and even then males battle each other for the female. Once courtship is over, she leaves immediately to lay her eggs.

One laying can exceed 10,000 eggs, yet predators devour some 8,000 of them unhatched. Adult mantises, fighting over territory, kill all but about ten of the 2,000 hatchlings, and in the end maybe three from the whole clutch survive to breed the following year.