Nether fossils are unique remnants found in the Minecraft game, specifically in the Nether dimension. They are used to craft bone blocks and can be obtained by mining certain blocks, such as soul sand or soul soil. These fossils resemble large skeletal structures and are often scattered throughout the landscape. In addition to their crafting uses, nether fossils serve as a visual reminder of the game's lore, hinting at the existence of ancient creatures. Players often seek them out for both their aesthetic value and practical applications in building and crafting within the Minecraft universe.