The Monster from The Ritual (will be referring to said monster as a she, as the director confirmed it was a she) screams Beast the Primordial to me.

She's a Namtaru Predator who's likely earned her Inheritance, seeing as she never leaves her Horror form, I'm assuming the one she took was the Merger. The forest is her Lair and the pagans in the film are her Cultists, the mummies in the attic her Heralds that earned eternal life in service to their master.

The Monster relies more on Nightmares than anything, Her kit includes Soldier's Heart, The Walls Have Eyes and You...