The Corruption of It

The Corruption of It is a biome located on the surface
 * It starts off small and continues to grow until has been defeated
 * It continues to grow during Invasions
 * It is notable for its meaty vegetation such as eyeball plants and horns growing out of the ground
 * The ground is a red meaty texture, and can only be mined with the.

NOTE: If Commander Vile is not killed, the corruption will eventually cover 80% of the surface, making it hard (for most classes) to go down below or back to surface.