The koshchey is created through Alzur's Double Cross, a vile ritual known to some sorcerers. It is a member of that infamous group of gigantic beasts that can cause destruction on a massive scale while killing droves of people. Neither a crab nor a spider, it is tough as nails. Even a witcher might find the soft meat inside hard to get at. The first koshchey was created by an ex-druid called Fregenal using either the Triangle Within a Triangle or Alzur's Double Cross and destroyed by Visenna using the Mirror Effect spell.