Pond Moss is a tier-three crafting material in Grounded and can be used to make weapons, armor, and decorations. This resource can also be used to create the valuable Sarah’s Charm. When equipped, this Trinket grants a chance for melee weapon attacks to repair the weapon. Similarly, when blocking attacks with a shield, there is a chance for the shield to repair itself. Since it is a tier-three material, Pond Moss cannot be acquired early on in the game. Players will first need to upgrade their combat abilities.

https://screenrant.com/grounded-how-to-get-use-pond-moss/