怨霊（おんりょう）
Onryō
A vengeful spirit, of the dead or sometimes of the living, that brings harm.
An onryō is a spirit with a grievance and the power to act on it. The idea is old: in the Heian period the court blamed plagues, fires and bad harvests on the angry dead of its own political victims, and the remedy was to honour them. The scholar Sugawara no Michizane, who died in exile in 903, was enshrined as the god Tenjin after a run of disasters was laid at his door. A spirit placated this way was called a goryō, an honoured spirit.
On the Edo stage the onryō became the wronged wife returning for her husband, and Oiwa of Tōkaidō Yotsuya Kaidan (1825) is the model every later ghost follows. The fox Tamamo-no-Mae becomes an onryō in a stone: the sesshōseki, the killing stone of Nasu, which destroys whatever comes near it until a monk breaks it. The harm such a spirit sends is called tatari.
Related yokai
Oiwa
お岩（おいわ）
Oiwa is the wronged wife of Tsuruya Nanboku's 1825 kabuki play Tōkaidō Yotsuya Kaidan — poisoned under the name of medicine, betrayed, and returning to pursue her husband. On stage, she emerges from a burning lantern.
Tamamo-no-Mae
玉藻前（たまものまえ）
In the fifteenth-century tale, Tamamo-no-Mae is the most learned woman at the court of Retired Emperor Toba. He falls ill, divination names her as the cause, and she flees to Nasu as a fox. The killing stone came later.
Shichinin-misaki
七人ミサキ（しちにんみさき）
In a tale told in Sukumo, Kōchi, seven women fleeing a political upheaval were caught at the border and put to death beneath an old cherry tree. Seven figures in white appeared there until the people began holding memorial rites.