Looking for semi-cheezy 70’s/80’s horror movie title

Fairly good movie I saw on TV in the early 90’s. Bunch of drunk teens go up to party in a spooky old haunted mansion and some demon-y thing comes out the cellar and starts killing them off. Only one kid escapes but he is then arrested and convicted for all the murders. Fast-forward twenty years and he’s being let out of prison. Outside the jail he meets and old private-eye type who tells him that he thinks the murders were actually committed by a demon-worshipping cult that is required to kill X number of people every XX years to appease the demon. So they go off looking for the cultists. So it’s swerved from being a supernatural movie to a crime movie. However as the plot develops it’s revealed that there IS a real Demon who kills X People every XX years. The timing of the killing has to fall on the one night of the year that the ‘ghost star’ is visible in the sky…. Thought the name might have been “demon star’ or something like that, but haven’t found anything by that name.