Lovecraft wrote genuinely creepy and disturbing stuff. It has been very memorable for anyone who has read it - including a number of other horror writers who later incorporated elements of Lovecraft's 'mythology' into their own work (some of them very popular). It has become a little like a virus. The more people that are touched by it the more it spreads.
It's from the short story "The Call of Cthulhu." I'm not a big fan of the pop culture view of it, but the story is exceedingly amazing. It was written by H.P. Lovecraft, an influential horror writer of the 20th century.