Movie with old man with long white beard holding some kind of light...?

This was back in the 1970s, possibly early 1980s. I remember there were a group of middle-aged men, in their 40s and 50s, going on a trip. They were going down a rappelling line. One of them got entangled in the rope. I don't remember if he was left behind for dead or he was helped. They came upon this cavern or underground area. There was an old man, long white beard reaching his knees. He was carrying some kind of a light, lantern, or something in both of his hand. Then the light started to shoot out of the contraption. The old man spins around with the light. Only movement he did was the spinning around. But his body was rigid. The light was either destroying or vaporizing anything in its path.