Most consider this to be a hoax, but in 1989, Russian scientists bored a hole into the earth and broke into a super-heated pocket which was well over 1,000 degrees in temperature. Recording devices lowered into the pocket picked up all manners of disturbing sounds, and those on site claimed a winged gas demon flew up from the gas pocket and escaped into the world.
http://www.therichest.com/rich-list/most-shocking/the-25-most-terrifying-urban-legends-in-the-world/
YOU'VE GONE INCOGNITO 