The Witch House was located near the town of Penmallow in Cornwall, England whose residents lived in fear of the manor. Dr. Strange sensed within it traces of ancient blasphemies. It's housekeeper was Blondine, who was the latest reincarnation of the High Priestess of Dagoth, of the evil city of Kalumesh which had been sunk by the seas.
The Witch House was actually a portal to Kathulos' living planetoid. Kathulos could animate the house which nearly killed Dr. Strange and is companions. To destroy the house, Dr. Strange was forced to call on the Vishanti, a godlike trio, for their assistance which finally shattered the house, reducing it to rubble.