Don't Go Near the Park(1979)

They were cursed to eternal life at the cost of their souls!

In the prehistory of man, 12,000 years ago, two members of a superhuman tribe abuse the treasured secret of eternal youth. They use the methods of ritual cannibalism on the children of their own tribe and when discovered by the 'Queen' of the tribe, they are cursed to an eternity of old age with no chance to ever die. Now, in present day Los Angeles, their only hope to recapture eternal youth is the ritualistic sacrifice of a 16-year-old female virgin. Their existence is discovered by an investigative reporter and a young runaway child and this leads to an unexplained and terrifying confrontation