Demon Rock, an important item used to build or improve armor and weapons in Wild Hearts, may be hard for players to get due to the item's limited spawn location. While the straightforward crafting system in the game requires a myriad of other materials in addition to Demon Rock, players will find that this particular item contributes to specific upgrade paths after a certain point in the story. The eight primary weapons seen in Wild Hearts will all eventually need Demon Rock to challenge the tougher Kemono seen in later stages of the game.

https://screenrant.com/how-to-get-farm-demon-rock-wild-hearts/