Board Thread:Questions and Answers/@comment-4557996-20140109011942/@comment-25345260-20140505211928

Caita72 wrote: Jagex comfirmed that demons aren't spirits like the biblical monsters. So maybe they get dirty it on in bed like other creatures? inb4Rosemary'sBaby

In full seriousness, this makes it that much easier to understand. It's just like humans, but more violent and on a larger scale.