The Legend of the Nine-tailed Fox (Kuniyoshi, from "The Magic Fox of Three Countries" series) :

When Abe built an altar in the garden to offer prayers for the emperor's recovery, Tamamo lept up onto the altar and appeared in her true form. In the image above, the nine-tailed fox appears on the altar; in the lower right a court lady attempts to kill her with a dagger.

Emperor Toba was a central figure in the unstable politics of the court in the 12th century. Retired Emperor Toba became engaged in a dispute with his oldest son Emperor Sutoku over who was to be the next emperor. This dispute led to a rebellion in 1156 that foreshadowed the Heike and Minamoto civil war of the 1180s that was to bring the Heian period to an end. After Emperor Toba abdicated (at the age of 21) he added considerably to the number of his concubines. One in particular, Fujiwara no Tokuko, was said to have exercised a powerful, malignant influence over him, encouraging the political intrigues that caused so much trouble during his time. This may have been the historical basis of the story.