Sienna's creator, Damien Leone, invested a lot of time into fully developing her as a character as he regretted leaving the first film's heroine Victoria Heyes underdeveloped.

The character originates from an abandoned film Leone was developing in the late 2000s, featuring the concept of a Valkyrie-angel warrior attired heroine battling Art.

LaVera spent months questioning Leone for preparation and developed a full binder of notes about Sienna—asking him who inspired the character and having him create a playlist that he believed Sienna would listen to.

The outfit was not complete by the time filming began, and it did not have lining; LaVera had to wear duct tape to hold the attire together throughout the shoot and even developed blisters.

In this film, Sienna (Lauren LaVera) is a teenage girl living with her widowed mother and her younger brother Jonathan following the death of their father.

[4] In this film, set five years after Terrifier 2, Sienna is released from a psychiatric hospital to live with her aunt, uncle, and younger cousin, Gabbie.

[4] The conception of Sienna Shaw dates back to 2008—with Leone envisioning an angel-warrior-attired heroine to battle Art the Clown for a feature-length follow-up to his 2008 directorial debut short film The 9th Circle.

[6] Leone wrote the character with mythic religious undertones, envisioning her as a teenage girl slowly transforming into the embodiment of an Old Testament angel that is the equivalent to Art's representation of a resurrected demon.

LaVera began receiving private messages from fans telling her that they intend to make either a costume based on it or a drag interpretation of Sienna.

[10] Collider's Raquel Hollman describes Sienna as the Wonder Woman of horror films and that she provides a "supernatural element" to the final girl trope due to her resurrection after death.

LaVera carries that motif through with dazzling star power, ending 2022 as its greatest final girl, a serious accomplishment given that she's following up Neve Campbell and Jamie Lee Curtis.

[16] Jaden Oberkrom of North Texas Daily praised LaVera, writing that her performance "immediately gets the audience invested in her character.

"[17] Dakota Mayes of MovieWeb writes that "Lauren LaVera breathes life into Sienna and plays her as a final girl like no other.

"[18] Writing for Comic Book Resources, writer Maddie Davis highlights the character's resurrection after death as making her notably different to prior horror heroines.