Prince of Darkness movie

A priest/a millionaire dies and leaves a diary and a casket containing a key. Another priest reads the diary and after visiting a deserted church discovers a large glass tube containing some kind of green swirling liquid locked away. The priest tells a Professor friend of the discovery and the priest, the professor and a couple of students stay in the church to research the tube. Their discovery leads to the fact that the tube contains the Devils son, and a prophecy that when the sleeper awakens the son will release the father. The tube is locked from the inside and the sleeper is beginning to stir. The students/priest/professor now have a battle to stop the Devil from being released but some of them are being taken over to aid the Sons cause...