Old Whateley, also known as Wizard Whateley, was a major character in Lovecraft's The Dunwich Horror.
It can be assumed that he summoned Yog-Sothoth to impregnate his daughter or that she was a type of sacrifice.
He was the "aged and half-insane father of Lavinia Whateley," about whom the most frightful tales of magic had been whispered in his youth". Dunwich gossips recall that "the hills once shook when he shrieked the dreadful name of Yog-Sothoth in the midst of a circle of stones with a great book open in his arms before him."
He and his daughter occupy a large farmhouse on a hillside, four miles from the Village of Dunwich, Massachusetts, and a mile and a half from any other dwellings. When his daughter was twelve, his wife died, through ill-explained but violent means.
He has a large collection of "rotting ancient books and parts of books" which he inherited through two centuries of Whateleys. He uses these to "instruct and catechise" his daughter as well as his grandson Wilbur. One such book was an incomplete version of the infamous Necronomicon.
He died of natural causes on August 2, 1924. Just before his passing he left Wilbur with the responsibility of looking after his twin:
"More space, Willy, more space soon. Yew grows- an' that grows faster. It'll be ready to sarve ye soon, boy. Open up the gates to Yog-Sothoth with the long chant that ye'll find on page 751 of the complete edition, an' put a match to the prison. Fire from airth can't burn it nohow."
Wilbur observed that the whippoorwills, dispersed shortly after his passing, signifying that the creatures did not take his soul.
His first name is never mentioned, though in Lovecraft's later work, Fungi from Yuggoth, he mentions a John Whateley. It is unknown if this is the same man.