The surprise episode, as reported by Slashfilm, centers on Necina, a young Shokopiwah hunter portrayed by Kiawentiio, who ventures into the forbidden Western Wood with her friends. Their ill-fated expedition quickly brings them face-to-face with the malevolent entity that has plagued Derry for centuries. While the episode expands on the lore briefly touched upon in the fourth episode of the main series, its true highlight is the long-awaited debut of one of Stephen King's most enigmatic and powerful cosmic beings.

Maturin, known in King's mythology as one of the two beings who created the universe (the other being It itself), has been a peripheral, often alluded-to figure in past adaptations. Andy Muschietti's It Chapter One and It Chapter Two films, along with the Welcome to Derry series, have peppered their narratives with subtle turtle motifs, such as the school mascot Bert the Turtle. However, "A Story of Derry" moves beyond mere Easter eggs, presenting the cosmic turtle in a tangible, albeit ethereal, form.

In the prequel, Maturin appears to Kino (Isabel Deroy-Olson), a medicine woman in training, during a dream sequence induced by smoking a mysterious 'Maturin root' powder. This mystical encounter allows Kino to communicate with the ancient entity, who imparts crucial knowledge on how to combat It: by utilizing shards of meteorite glass to create a new prison for the evil presence. The depiction is brief and appropriately otherworldly, making its introduction feel organic within the Shokopiwah's spiritual practices and the dream-like context.

The inclusion of Maturin is a monumental moment for King aficionados, as the entity plays a much larger role in the overarching narrative of The Dark Tower series. Its appearance in It: Welcome to Derry not only enriches the prequel's lore but also hints at a broader, interconnected Stephen King cinematic universe. With filmmaker Mike Flanagan actively developing a Dark Tower TV adaptation for Amazon, which holds the rights to that particular saga, the groundwork laid by It: Welcome to Derry could pave the way for future, more prominent appearances of Maturin and other cosmic elements from King's vast imaginative world.