"The Great Race of Yith are beings of enormous intellectual and psychic powers that once dwelt on the dying world of Yith."
"They escaped the destruction of their home planet by transferring their minds to the bodies of a species native to the Earth in the far distant past."
"They lived on this planet for 200 million years or so, in fierce competition with the flying polyps, until this enemy finally destroyed their civilization near the close of the Cretaceous era (about 65 million years ago)."
"In the bodies they inhabited on the Earth, they were tall and cone-shaped, rising to a point with four strange appendages – two terminating in claws, a third in a "trumpet", and the fourth, a yellow globe which functioned as a sensory organ."
"The unique ability of this scientifically-advanced race was to travel through time by swapping minds with creatures of another era. This allowed them to satisfy their interest in human culture, science, and occult beliefs."