The Ghost Auroch is the legendary animal in Francia. It is found in Amienois. This works like any other fight with a large animal; however, half way through the fight the bull will run away from you and you will need to chase it down. In the next area it will regain health until you attack it. If it regains enough health and you don't kill it quick enough it will run to another area to heal again. Once defeated, you will earn your achievement / trophy.