David Wenham's last scene in the film was difficult for him because he is a bit claustrophobic, but according to director Kiah Roache-Turner, he powered through it like a trooper.
Composer Michael Lira had some fun with the choir's lyrics of Nekrotronic. Multiple instances of Internet terminology are recited backwards throughout the film including: "mar ga tad" (datagram), "dah re nab" (banner ad), and "noh ki to me" (emoticon). During the finale, as a demon rises from the plasma pool, a choir is heard chanting Latin: "stagnum calidum" (hot bath/hot tub) and very quietly, "flexilis anatis" (rubber duck).
The original concept was to be ghost hunters trapped in a haunted house.
The film premiered at the Toronto International Film Festival in September 2018 as part of the Midnight Madness line-up.
During the final credits, a female demon does the reverse spider walk, which is likely a nod to L'Exorciste (1973), where the main female character, Regan (Linda Blair), is possessed by demons and does the same thing.