Witch Creek Road S3 E23 Explained (Spoilers)
The episode opens with Tenebris, using the smoke from the fire, to create a body for himself. He's much larger than we've previously seen (in Episodes 3 and 21). The main Wolf turns to Teberis, and, with slight amusement, begins to ask Tenebris, "And who might you be?" She's unable to finish this sentence; Tenebris grabs her by the head and slams her into the bookshelves.
The Serpent reminds Tenebris that, once the Serpent leaves, Tenebris will only have a few minutes. Tenebris smiles and replies, "I'll make the best of it."
We shift to Shaleeta, who's home alone. She finds herself in the midst of a panic attack, and suddenly "is running to the bathroom to vomit." We learn that Shaleeta used to get panic attacks sometimes, brought on by "an upcoming test or a looming deadline,” but that these stopped after the camping trip the previous year (see Season 1). On the camping trip, Shaleeta's boyfriend, Ryan, "was murdered; Shaleeta survived. And the big velvet curtain that covered the world was pulled back. There were monsters in the darkness. Suddenly tests and assignments seemed small."
"And then there was the notebook. The promise of revenge. She studied and became stronger, and eventually she learned the truth... That there had originally been a different demon that hunted them through the woods, and she had already achieved her revenge. And, in doing so, Shaleeta had taken its place. She would become the monster in the woods. She would become the monster behind the curtain of the world. And the only way to keep the original Wolf from returning was to complete the cycle: to kill Ryan and send herself on a path of revenge and power." (See Season 2 Episode 22).
Shaleeta smells smoke and runs through the house; she finds nothing out of the ordinary. "She feels her ribs break. And she slumps to her knees, trying to breathe through the pain." That's when she hears screams emanating from within her head. "She looks up, and the corner of the room is throbbing"; she walks through it, saying "a few words she only vaguely understands, and finds herself standing in a nightmare version of the old man's house. It's on fire. The old man is dead." And the Wolves are fighting against a creature made out of smoke.
Shaleeta realizes that the screams are coming from the Books of Shadows, and she snatches it away from the approaching fire.
Wolf Shaleeta approaches human Shaleeta and tells her to leave, telling her something is wrong. Shaleeta ignores the Wolf version of herself; she understands something the Wolves don't. She understands that the smoke is tethered to something, but the tether is far away. She understands that the smoke is barely holding itself together.
Shaleeta begins to chant, hoping to disrupt whatever is still holding the smoke together, but before she can finish the smoke stabs her through the throat. Just then the sprinklers go off, and the smoke bids the Wolves farewell, leaving Shaleeta to die on the floor.
With Shaleeta dead, her Wolf version disappears from existence, and the original Wolf returns to take its place.
TEBERIS' TETHER: Though not expressed, the Serpent and Tenebris are bound to one another. While the Serpent is in close proximity, Tenebris is fine, but Tenebris is unable to maintain his form if the Serpent leaves. This is why the Serpent reminds Tenebris that, once the Serpent leaves with Hailey, Tenebris will only have a few minutes.
SHALEETA'S CONNECTION TO WOLF SHALEETA: Everything Shaleeta experiences in her house is directly connected to what's happening to the Wolf version of herself. The panic attack occurs when the old man dies (this is also why Wolf Shaleeta is nowhere to be seen at the end of Season 3 Episode 11 - she's trying to compose herself and not appear weak in front of the other two Wolves).
When Shaleeta smells smoke, it's because Wolf Shaleeta is present within the burning library of the old man. And when Wolf Shaleeta gets injured, Shaleeta feels her own ribs break.
WOLF SHALEETA'S REACTION: When Wolf Shaleeta sees human Shaleeta arrive, she understands that something is wrong. She pushes Shaleeta toward the corner of the room, telling her, "You need to leave. This is all wrong. I don't remember any of this." Wolf Shaleeta understands that, by human Shaleeta being there, Wolf Shaleeta should have the memories of human Shaleeta being in this room - but she doesn't.
SHALEETA CONNECTION TO THE BOOK: When Shaleeta picks up the book, she notes that "The eyes are still closed, and she breathes a sigh of relief." Shaleeta understands the importance of the book's eyes remaining closed (and the danger it would pose if the eyes ever opened).
Shaleeta is also connected to the book because it's through studying the book that she's been gaining her power. This is why Shaleeta can hear the book when it's in distress.