Psychic Self-Defense by Alexandra David Neil

occultist Dion Fortune describes how she once accidentally formulated a werewolf. Alexandra David Neil became obsessed with creating a tulpa of her own. She retired to hermitage and devoted every waking second to creating her tulpa. Her monk slowly took on a personality of his own, performing tasks she had not instructed him to perform. He wrote a Mustang horse that nobody else was able to ride,. the wildest in the camp was now calm and obeyed the tulpa's commands perfectly. Eventually he grew lean and gaunt, his expression cool and malignant.