User blog comment:Sasha Dawg/That's Strange... Is This a Glitch?/@comment-80.194.6.210-20120729183254/@comment-5292086-20120730184349

To you and the person above you, I have discovered that ebonstone and the whole corruption and hallow in general can only spread in the overworld, so I won't have a completely corrupt underworld. Btw, I have faced hell monsters in my artificial corruption. So no, not only corruption monsters will spawn.