Liam Gavin had watched a documentary about Aleister Crowley performing the Abramelin ritual at Loch Ness.

The ritual, drawn from a fifteenth-century grimoire known as the Book of Abramelin the Mage, is an attempt to summon one's Holy Guardian Angel through eighteen months of isolation, moral purification, prayer, and encounters with demonic entities. In the film it takes eight months.

Gavin had been working as a storyboard artist and making short films for years when he sat down to write a low-budget debut feature.

He knew the standard formula - get eight people in a house and have them kill each other. He set himself a harder challenge: one location, two people, and a premise that would require those two people to be believably trapped together for months.

A DARK SONG (2016) was filmed in a semi-abandoned house in North Dublin - technically in the middle of a housing estate, which is why the film never looks out of any windows. The budget was approximately $50,000.

The ominous cloud formation in the film's final sequence appeared spontaneously while the crew was doing pickups in the Wicklow mountains. Gavin made a frantic dash to get cars in position before it disappeared, with walkie-talkies that had thirty seconds of battery left. It was not a composite shot.

As might be expected, some occultists in the audience took issue with perceived inaccuracies in the film. Regardless, this is one of the creepiest, most realistic portrayals of magic ever put on screen.