Demon Lover is a little known example of how - in the early 1970s - Steeleye Span were often able to capture the uncanny and supernatural style of Romanticism that was pioneered by Coleridge. The chilling lyrics are derived from an ancient Border Ballad - and seem to refer to a demon who masquerades as a beautiful fairy in order to entice-away a young wife.
The strands of English folk music have included this uncanny element; although not many performers are able to treat it with the seriousness required for it really to hit home. In Steeleye Span's case, it was specifically the lead guitarist and vocalist Robert Johnson who brought this into the band (e.g. King Henry, Alison Gross, Thomas the Rhymer, Long Lankin).
This mood is quite easy to for modern people ruin by any taint of irony or commercialism - and it only lasted for the first four albums of Johnson's membership of Steeleye, being largely spoiled by the producer Mike Batt - after which Johnson left Steeleye to make a 'concept album' of Lord Dunsany's novel The King of Elfland's Daughter.
As I have often remarked, it is a sadness to me that this early 70s Romantic Revival, of which The Watersons, Steeleye Span and The Albion Country Band were a part; and which was quite genuine in terms of its picking-up the impulse from Blake, Coleridge and Wordsworth; failed to kick-on by rejecting and failing to Romanticise Christianity.
(Many of the adherents seem to have had neo-pagan, anything-but-Christian, sympathies - although the Watersons recorded many gospel revival songs, and some Christmas carols were popular.)
Instead, this reborn Romanticism was (yet-again) appropriated (especially by journalists, critics and scholars) and distorted/ diverted into Leftist politics... It is hard to blame musicians for failing to do what people seemingly better equipped also failed to do, and the true direction of which was, and is, novel and far from obvious; nonetheless it is a sadness.
While I have enjoyed plenty of folk music since this time - it always lacks the implied depths and serious intent of those early years.