The Elder Things (also known as the Old Ones and Elder Ones) are an alien race in the Lovecraft Universe.
They were the first alien species to come to the Earth, colonizing the planet about one billion years ago. Their bodies were incredibly tough, capable of withstanding the pressures of the deepest ocean and the harsh vacuum of space. They were also capable of hibernating for vast epochs of time.
They built huge cities, both underwater and on dry land. They may be responsible for the appearance of the first life-forms on Earth.
It was the gradual cooling of the planet during the last ice age that spelled their doom. Retreating to their undersea cities deep in the ocean, they would thereafter have no further dealings with the outer world.
Quote from the Necronomicon:
"Six feet end to end, three and five-tenths feet central diameter, tapering to one foot at each end. Like a barrel with five bulging ridges in place of staves. Lateral breakages, as of thinnish stalks, are at equator in middle of these ridges. In furrows between ridges are curious growths – combs or wings that fold up and spread out like fans. . . which gives almost seven-foot wing spread. Arrangement reminds one of certain monsters of primal myth, especially fabled Elder Things."