This was really the seminal movie that pioneered the Babadook genre.One could argue the short film

This was really the seminal movie that pioneered the Babadook genre.
One could argue the short film it was based on, 2005's "Monster", was actually the first Babadook movie but discerning eyes will notice this is clearly a film about a "Monster", not a "Babadook".

"The Babadook" is a psychological thriller horror film about the titular "Babadook", also known as "Mister Babadook", a creature from a children's book that seems to have come to life (or is this simply a figment of our main characters' imagination and deteriorating mental state?). As we navigate through the twisting paths of life - and as secrets, fears and insecurities build up in the babadooks and crannies of our cranial cavities, we may too start to wonder if our monsters are real. Regardless of whether we can see them our not, there's something powerful in being able to confront the "Babadook" we see in the mirror, and show him the Babadoor.