H. P. Lovecraft: The Colour Out of Space: What unknown being is lurking out there?

“The oldest and strongest emotion of mankind is fear, and the oldest and strongest kind of fear is fear of the unknown.” This creepy horror story is one of the best written by Lovecraft in my opinion. What unknown being is lurking out there? What entity arrived in that meteor? Never described exactly, yet he manages to let your own imagination smell and taste it in this story.