Source: Tales from the Fens (1963)
When monks tried to build a church at Southery, the locals (who lived by robbing boats) killed them. The Baron of Northwold sent a pack of Wolfhounds to guard the new monks.
The hounds ate the locals, then turned on the monks. One giant bitch-hound survived in the fens and gave birth to a monstrous pup (“neither dog nor wolf”). This beast protected the Fenmen for years.
The Haunt: If you go out at midnight on May 29th (Southery Feast), you will hear the Wolfhound howl. Seeing it means death within a year. The cornerstones of the ruined charnel house are said to be gnawed by the ghost dog trying to get at the bones.