Interesting Easter Egg - just after the fire ritual scene, Marsden sees a demon on the balcony of the house. To the right of the demon is an oval window. And in that window a large human eye appears. It blinks open then vanishes - all in a few frames. That eye matches the close-up of the daughter's eye when she is on the surgery table in the hospital near the end of the movie. This seems to be a clue that the characters are somehow in the daughter's dream as she lies dying. As if all the characters are sharing a dream in a sense.
Near the end of the fire ritual, just after they all finish chanting 'I call death!' the last voice heard far off in the distance is the dead daughter chanting 'You call death!'
Near the end of the movie, when Marsden has his shirt off and he is walking through the basement door Into the Light, the stitches on his face and body are in different locations from the previous scene where he first took his shirt off.
(at around 4 mins)When Marsden is speaking to the Real Estate Agent, the blowing wind reveals a microphone pack strapped to the back of her leg just above the knee.