Fibrous Taint (Thaumcraft 5)

Fibrous Taint is a block from Thaumcraft 5. It can be found in Tainted Lands Biome, or is spawned randomly by the decay of Flux Goo. Fibrous Taint will spread if there is Vitium in the aura, growing onto blocks, and converting them into their tainted variants. It will convert Dirt and dirt like blocks into Tainted Dirt, Stone and other rocklike blocks into Tainted Rock, Wood into Taintwood Log and Leaf blocks into Crusted Taint. Each of these tainted blocks can spawn more Fibrous Taint and, with the exception of Tainted Rock, acts like Fibrous Taint and can taint adjacent blocks.

Fibrous Taint will not corrupt blocks with a hardness of more than 10; the only vanilla block with this property is Obsidian. It also has special behavior regarding some blocks- Taint will not convert Torches, making it possible to light tainted areas. And on Glass, Fibrous Taint will not spread from Glass onto Glass, making it possible to build a two high wall of glass blocks, which will prevent the spread of Fibrous Taint over the wall.

As Fibrous Taint spreads, it converts the area its in into Tainted Lands Biome, but the Tainted Lands Biome itself does not spontaneously generate Fibrous Taint or taint any blocks.