User blog comment:-Merca/MONEY FARMING 2: The Eye of Cthulhu/@comment-4781346-20120309062751/@comment-4847179-20120309124000

if you talk about these guys then OF COURSE. they are bosses and only spawn once by themselves per world when you've met the conditions (Check The Page) if you're talking about Demon Eyes, then i think it's strange. try build a Demon Eye Farm high enough over the ground so you can't see the ground. if i knew how to take screenshots i'd post one in the blog of my Demon Eye Farm.