When Father Blackwood attempted to poison the Church of the Night members and run away at the end of Chilling Adventures of Sabrina Season 2, it was a significant turning point. After a long stretch of cloaking himself in righteousness, Blackwood had finally gone full evil. In Part 3 of the series, he did just that, not only threatening the lives of the Spellmans but honing his skills in a new sort of magic. But what was in Father Blackwood's egg that he opened in the series' final moments? It's not looking good for Sabrina and her crew.
Warning: Spoilers for Chilling Adventures of Sabrina Part 3 follow. The egg Father Blackwood hatched at the end of the finale came from Scotland, deep in the lake where the Loch Ness monster is said to live. At the beginning of Part 3, details about it were scarce, but over the eight-episode arc, fans learned some of its properties. For one thing, it can bend time: While Prudence and Ambrose experienced the passage of a few months, for Blackwood and his twins, it had been 15 years.
The egg also helped Sabrina time-travel, with the assistance of the powerful Unholy Regalia, to turn the events of this season upside-down. It even created a time paradox during Sabrina's use of it, but that doesn't seem to be the egg's fault — just Sabrina's usual teenage hubris.
So what was in the egg, and what will it do now that Father Blackwood has let it out? The egg is somewhat see-through, enough that one can see a vaguely fetal shape inside. Once the egg is opened, what's left behind looks akin to oversized maggots. So, there aren't really any clues there. However, the key may lie in a phrase Blackwood uses several times throughout the season: The Eldritch Horrors. The series never actually spelled out what its version of The Eldritch Horrors is, but the "eldritch" trope, popularized by H. P. Lovecraft, usually refers to "a type of creature defined by its disregard for the natural laws of the universe as we understand them." In many horror stories, this is an alien being from outside the dawn of time; it is almost always left somewhat ill-defined so the audience will use their imagination to fill in just how terrible it is.
In CAOS' case, the mystery being will most likely be some sort of satanic demon, but so far, it's sticking to the "ill-defined" definition quite well. As Mambo Marie said to Zelda in the finale's closing moments: "There's a darker force on the horizon," and Father Blackwood just let it out to roam free in Greendale.
Chilling Adventures of Sabrina Part 3 is on Netflix now.