Sm Tree Banshee - Tumblr Posts
The Tree Banshee theory
This is a theory predicting the role of Spooky Month's most enigmatic monster, one many fans might not even know about yet, so sit back and enjoy!

Watching HS for a second time, Gregor's pose here stuck out to me, so I went back to check my hunch...

Yep, he's in the same pose as the figure on the left wing of the gate. But what about the tree like figure on the right wing?
Well, for that, we turn to the movie theatre, many fans know about the demon priest poster that foreshadowed HS back in TT, well we see a very interesting poster for a second in episode 6

"The Forest Sight", huh?
Now for the clencher, we turn to an image from the arg

The same eye patterns, and a ghoulish being I've come to call the Tree Banshee, you might remember it for it's scream in TT or for an illustration of it in the book from the TT arg.
I believe this entity also somehow benefits from sacrifices made to Eyes and that it will be a/the major monster of a future episode, which lines up well with my idea of Roy's episode being about him chasing Skid and Pump into the woods, where they get lost.
More proof of the Tree Banshee theory
So, we know that the cult influenced the appearance for the church, with the diamond shaped window on the front door, so there's good odds they were responsible for this

A stained glass window depicting what appears to be a crucifixion as a person being turned into a tree, which further fits my idea of the banshee acting as a warden of sacrificed souls.