Talk:Boss Monsters/@comment-175.38.233.25-20121103045609/@comment-4674838-20121103054524

The message about a "mysterious presense" can occur when you smash a Shadow Orb in the corruption, but it can also sometimes happen at random. It's sort of like a warning that the Eye of Cthulhu *might* spawn.

About Cthulhu: that was an idea in the development stage of the game, you can read about it on the Cthulhu page. But no, it won't be added into the game, the developers announced the game was complete back in February:
 * http://www.terrariaonline.com/threads/my-fellow-terrarians.81455/
 * http://www.terrariaonline.com/threads/my-fellow-terrarians-pt-2.82165/