The mantis is a large predatory arthropod about 3 blocks tall. It spawns in the Overworld and the Crystal dimension. It does 8 hearts of damage by grappling you with its claws. It attacks anything nearby but dies quickly to bosses.
Have a use of diamond armour with an amethyst sword. It drops the mantis claw for Big Bertha. It will also drop some stuff that could be useful as well.