Prince of Darkness 4K 1987 US

A group of scientists finds an unusual vessel while exploring an abandoned church. With the help of X-rays they manage to determine that the vessel is about 7 million years old, and that it can only be opened from the inside. It contains some incomprehensible substance - a liquid diamond created by some mysterious force.

An ancient manuscript says that in this diamond rests Satan himself or his spirit. As a result of experiments, the devil's power, released from the vessel and scattered in space, begins to possess the researchers, turning them into Satan's slaves.