It could be that whatever pack they are playing has a conflict between taint biomes and ominous woods, and it shows as the woods, but has the characteristics of a taint biomeI'm pretty sure ominous woods don't spread. Tainted Lands/forest do however - are you sure it isn't that?
Or you could nuke the living daylights out of the biome... that'd get rid of all the taintedness... and everything else, but it wouldn't spread anymoreThe Thaumcraft tainted lands biome is driven by the spread of fibrous taint on the surface.
This should be easy to spot. And it is 'easy' to physically block with water or any non solid block such as glass or fence.
Otherwise, in addition to the above, if twilight forest is in the pack it also adds a magical sapling that creates enchanted forest in a ~20 block radius.
The Thaumcraft tainted lands biome is driven by the spread of fibrous taint on the surface.
This should be easy to spot. And it is 'easy' to physically block with water or any non solid block such as glass or fence.
Otherwise, in addition to the above, if twilight forest is in the pack it also adds a magical sapling that creates enchanted forest in a ~20 block radius.