Imagine a drowner that burrows tunnels, climbs trees, is more vicious than usual, and when ambushing its prey, it does so with many of its kin. Now you have a good Idea of what a nekker is. These primitive creatures are the bane of the wilderness - the inhabitants of forest villages fear them, and animals give their nests a wide berth. Nekkers are social creatures, gathering in something akin to tribes, for they can only repel the attacks of stronger assailants en masse.
Witchers can use their full range of skills and techniques when fighting nekkers. Signs, bombs, poisons and oils that augment bleeding are all extremely effective against the beasts. Nekker nests are best destroyed with Grapeshot bombs.