Great Race of YithWarning: Spoilers follow
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.