Keziah Mason is a witch who studied the secrets of inter-dimensional travel.
During the Salem witch trials of 1692, an old woman by the name of Keziah Mason was arrested for her suspicious behavior and seeming insight into other worlds. In her testimony to Judge John Hathorne, She confessed to having signed her name in the Black Book of Azathoth, and of her secret name of Nahab. She later disappeared mysteriously from Salem.
She is described as having a "bent back, long nose, and shrivelled chin" and has a "croaking voice".
She has an animal familiar; the rat-creature Brown Jenkin, which she trusts to carry messages between her and the devil. She feeds this creature on her blood.
When studying physicist Walter Gilman took a room in her house she revealed to him the secrets of inter-dimensional travel in the hopes of taking his soul.