A special fossil from the Rotten Vale. Unspeakably ominous.
How to get Wicked Fossil
This item can be obtained by finding the unique gathering point spawning only during "Upsurge: Ancient Fossils" in the Rotten Vale. Gathering it for the first time will unlock the Big Bite Burger ingredient at the Canteen.
Upon exiting Camp (1) jumping off the cliff or climbing down, head right staying close to the left wall. A short slope to the west is present, so go down without jumping. Turn around and you should be here, right in the middle of the path: