In 1985 I was 15, and already a big horror movie fan. With Evil Dead, Halloween, Friday 13th, Italian horror ... the genre was dynamic. Then, reading Mad Movies, I see this very gore movie inspired by a short Lovecraft tale, coming soon.
I go there at 2pm, watch the movie and end up seeing it 7 times in 3 days. The cast gives an insane (!!!) performance, especially Jeffrey Combs of course, but having Bruce Abbott try to keep his sanity and stay alive in the horrific events. Barbara Crampton will be mainly remembered by being licked by a severed head, but she does a nice "normal" character. The couple try to save what they can (sanity and life) and are quite a counterpoint to West and his madness of overcoming death, whatever consequences there may be.
Most scenes are in the Arkham faculty, some at Dan's apartment. This also enhances the madness of it all, with a regular setting where usually nothing wrong could happen.
The "gore" SFX still are vivid in my mind. So OK more modern SFX are done now, but those rubber body parts with liters of blood were really efficient, and I'll add "physical". Those computer generated very often lack the practical physicality of holding a severed hand or head they do now (must be a challenge for the actors to interact with nothing beside a green sceen.
Overall these elements create a powerfully entertaining movie.