An original, first-rate example of atmospheric horror, 'Dies Irae', like Rahul Sadasivan's last two outings, ‘Bhoothakaalam’ and ‘Bramayugam’, relies on pure, gimmick-free horror that constantly toys with our imagination. Here's a list of 20 films that explored similar themes and ideas in different ways. (Curated by Sajin Shrijith)