I've been trying to track down this story for years now.
It's a short horror/fantasy story from the 1980's about some kind of demon that lives in an ink bottle. I believe a writer is using the bottle of ink to write stories and the demon lives off the creative energy - or perhaps I'm getting that confused with some other story. I particularly remember a creepy scene where the tiny demon is licking the ink off the writer's pen with a long tongue. At any rate, the story ends with the demon killing the writer, with his pages of writing filled with blood/ink spatters and tiny footprints.
Lisa Tuttle comes to mind as an author but I can't find anything in her list of stories that matches this. Anyone? I believe I read this in either Fantasy and Science Fiction magazine or Asimov's Science Fiction mag or Analog - one of the monthly magazines from back then.