Is a Novigrad side quest with suggested level 25.

Talk to the halfling Brean Hotsch to start the quest. You can increase the reward by some 40 crowns. After talking to Hotsch, talk to the nearby survivor of the attacks.

Head to the Hotsch's woodcutter's hut. After arriving, use your witcher senses to find the clues from the woodcutter's wagon. Follow the trail of the wagon using witcher senses. You may encounter Nekkers, and a Nekker warrior along the trail.

After finding the wagon, investigate the site using witcher senses. There will be two sets of blood stains, footprints, and claws on a rock. After those clues, witcher senses will show the footprints leading towards a dwarf. The set of bloodstains will lead to another dwarf. From these clues Geralt determines it's a Leshen monster.

You can use some "Relict Oil", if you have it, to make your upcoming fight a little easier.

Head to each map marker until you find the leshen totem. After destroying the totem, the Leshen will appear.

After dealing with the Leshen, head back to Hotsch to collect your reward.