Ebonthorn

Ebonthorn is The Corruption's most aggressive form of terraforming. It can begin growing from any patch of ebongrass, and has nearly gravity-defying rigidity; allowing the plant to grow up to six feet in any direction. It often grows in a mazelike pattern, though breaking it is surprisingly easy and its remains don't cause The Corruption to spread further.
However, beware being too close to ebonthorn, as it is hard enough to pierce armor, though that may account for how brittle it is. Ebonthorn does not produce ebon spores, and has to touch other plants or terrain directly in order to spread the condition.