The Gates of Hell trilogy is the unofficial name for a trilogy of films directed by Lucio Fulci.
[1] While the films aren't direct sequels they are thematically connected.
[2] All three films star Catriona MacColl as a leading character, were written by Fulci and Dardano Sacchetti with Giorgio Mariuzzo co-writing The Beyond and The House by the Cemetery.
[3] City of the Living Dead and The Beyond were both scored by Fabio Frizzi[4][5] while The House by the Cemetery had a score composed by both Walter Rizzati and Alessandro Blonksteiner.
[4] Eibon Press published comic adaptations of the films.