The Demon Lover (1977) 
The Demon Lover (AKA: Demon Master) is a surprisingly fun little entry into the satanic horror sub-genre.
The film centres around a group of impressionable teens who are members of a satanic cult headed by high priest Laval Blessing. One night whilst parting and drinking at Laval's 'castle' the group confronts Laval about his practices as leader, which ends up with them all walking out on him. However, you should never defy a high priest in a pact with Satan and who also has psycho-kinetic powers. Laval in a rage at his followers' abandonment conjures up a demon and uses his dark magical influence to insight his revenge.
The kills come thick and fast, and there was enough violent bloody kills, possession and manifestation effects along with plenty of cult iconography and chanting to keep me entertained throughout. A deep piercing electro score adds to the events nicely and the short running time means that the film never overstays its welcome.
Cheesy and a little OTT it may be, but The Demon Lover is also a hell of a lot of fun.