Contract: The Creature from Oxenfurt Forest is a Novigrad side quest with suggested level 35. It can be picked up from the Oxenfurt notice board, or by talking directly to the mercenary, Hans.

After picking up the contract, talk to Hans for more information on the contract, and you can also increase the reward.

After talking with Hans, head to where the monster attacked, and examine the area using witcher senses. Near the center of the map marker area, you will see a body, and a bloodstain, and slightly north of there will be part of another body, and more bloodstains. Follow the bloodstain trail. You'll encounter a pack of wolves on the way that you must deal with. Continue following the trail using witcher senses. When the trail stops, examine the final blood stain, and Geralt determines he should follow the sound of the ravens. Keep heading forwards and map marker circle will get smaller as you get closer, and you will eventually come across the nest, with the remaining body parts. Examine the body to find the mercenary contract. Read the contract, this can increase the reward you will receive when you hand in the quest.

Wait/Meditate until dark, and then the archgriffin will attack. The monster is an Archgriffin named Opinicus. Hybrid Oil will be useful in the fight. You can also easily bring it down when it swoops at you by using a blast of Aard.

After dealing with the monster, return to Hans to collect your reward. If you found and read the mercenary contract you can increase the reward amount further.