Fake animals and villagers that appear suspiciously fast near mines.
At Corruption Level 1, disguised fake animals, villagers and creepers occasionally appear near mines, moving with an unnaturally fast, suspicious speed.
These are not separate mobs, they are the Skinwalker itself, wearing another creature's shape rather than its own.
They are timed to disappear on their own, and now vanish immediately the moment World Corruption advances past Level 1.