Great Race of Yith

In the fictional Cthulhu Mythos of H. P. Lovecraft the Great Race of Yith are mental aliens that occupied a curious Earth native species and lived on the planet for 200 million or so years before they were destroyed by Flying Polyps[?] 50 million years ago.

On the Earth they were tall and cone-shaped, with four strange appendages terminating in claws, 'trumpets' or a yellow globe. The unique ability of the scientifically advanced race was to travel through time, by "body-switching" with a creature at any point in time. This allowed them to satisfy their interest in history. Occupied beings, now in a Yith body, are simultaneously queried for their knowledge.

They are fully described in The Shadow Out of Time by Lovecraft.