The Great Race of Yith are an alien race in the Lovecraft Universe. They are capable of projecting their consciousnesses across time, inhabiting the bodies of individuals of other species and swapping their minds with their own. At some point in the distant past, they abandoned their original bodies for those of a species living on the primitive Earth, and built a flourishing civilization on the planet in their new conic bodies.
They went to war with the Flying Polyps and the Elder Things. The Yithans were initially successful in the war against the flying polyps, and trapped them under Earth. They eventually lost the war but survived by projecting their minds into an insectoid race that will one day inherit the Earth after mankind.