Mysterious Tracks is a Witcher Contract Quest in the Witcher 3 Wild Hunt.
1. The quest is available from the Lindenvale Notice Board.
2. Speak to the Lindenvale hunter regarding the quest. The reward given on this page is attainable after haggling.
3. Follow the quest marker and examine the carcasses of the wolves. Examine the nearby tracks and follow them using witcher senses.
4. Geralt will eventually discover the lair of the beast which is set on a sharp cliff face. Go round and look for a cave entrance near the large tree.
5. Drop down into the cave from the newly discovered entrance. The fall can hurt!
6. Examine the fiend carcass (whilst looting the cave for valuables) and Geralt will comment on the need to lure the Chort. The Chort lure formula should then appear in the alchemy tab (it didn't for me because I bought the formula from the merchant in Lindenvale). The fiend dung required for the lure is available in two piles near the cave entrance and the inaccessible cave exit (which will hurt Geralt when he leaves).
7. Make the lure (there's enough crow's eye in the vicinity), equip the item in the pocket slot and then use it in the four indicated areas.
8. Return to the cave for a cut-scene.
9. Kill the Howler. It's a named chort and vulnerable to Relict oil. The cave is small making evasion of the chort's charge attack slightly difficult so the Quen sign is strongly advised. Its attacks inflict bleeding. If attacked from the flank or rear it takes a while to turn around and face Geralt.
10. Once it's dead, loot the carcass for the Chort trophy, Chort mutagen and a unique 3-slot sword.
11. Return to the Lindenvale hunter for the agreed reward to finish the quest.