Ninja Wars (1982)
Martial-arts/historical drama film originally released in Japan as Iga Ninpo-cho, Ninja Wars is a marvellous (or marvellously bad, depending on your tastes) adaptation of Futaro Yamada's 1958 book of the same name. Ninja Wars features players from Sonny Chiba's Japan Action Club, and covers the historical destruction of the Great Buddha of Todai-ji Temple by warlord Danjo Matsunaga in late-sixteenth-century feudal Japan.
A mysterious wizard named Kashin tells Danjo that whoever wins the heart of Lady Ukio will "conquer heaven and earth"; being the stereotypical evil villain, Danjo naturally sets out to score some tail and extend his power at the same time by bedding Ukio. In order to make her love him, he has his magi mix up a special love potion from ten herbs and a virgin's tears, in the much-prized Spider Tea Kettle. His evil plan involves kidnapping the hero's fiancée, switching her head with her twin sister's virgin body (with copiously-flowing fountains of blood spurting from their necks, the natural consequence of decapitation).
I won't spoil for you the ending by explaining it here, but I will mention this: if you watch the American VHS release from the mid-1980s, the movie won't either. Luckily, the recent Sonny Chiba Collection DVD series has restored the film to its proper form, fixing a host of inexplicable cuts, horrible dubbing, and other cinematic faux pas; restoring it to its deserved glory. The American cut has, nonetheless, established a cult following of its own, and if you can handle worse-than-Manos fare, it's worth a viewing if you can find a copy in the Blockbuster bargain bin.