Kiernan Shipka on Riverdale ! Sabrina Spellman Is Summoned to Rivervale by Cheryl Blossom

Kailey Schwerman/The CW

Sabrina Spellman has landed in Rivervale.

PEOPLE has the exclusive first look at Kiernan Shipka's guest appearance in the Dec. 7 crossover episode between Riverdale and Chilling Adventures of Sabrina. The fourth episode of Season 6, titled "The Witching Hour(s), is part of the CW drama's special five-episode event.

The penultimate episode will explore the supernatural genre as Greendale's witch Sabrina and Cheryl Blossom (Madelaine Petsch) team up on a dangerous spell.

"As Bailey's Comet passes over Rivervale, Cheryl and Nana Rose (Barbara Wallace) revisit the tragic stories of the Blossom women through the years. Meanwhile, the once-in-a-lifetime celestial event prompts Cheryl to summon a familiar face to Rivervale – Sabrina Spellman," the episode's description reads.

News of the crossover, directed by James DeWille and written by Arabella Anderson, was first shared in October by executive producer and creator Roberto Aguirre-Sacasa.

"We've been talking about having Sabrina visit Riverdale since season one, so it's thrilling that this is finally happening, as part of our Rivervale special event," Aguirre-Sacasa said in a statement shared with PEOPLE at the time. "It's also perfect that she shows up to help Cheryl Blossom during her hour of greatest need. Everyone on set lost their minds — I think fans will, too. It's really fun and special."

RELATED: Kiernan Shipka's Sabrina to Appear in Riverdale Season 6 for 'Years-in-the-Making Crossover'

Kailey Schwerman/The CW

Netflix's Chilling Adventures of Sabrina, which was the spinoff of Riverdale and a reboot of 1990s sitcom Sabrina the Teenage Witch, concluded in 2020 and the titular character died in the series finale.

The Rivervale special event, which has been playing with the idea of alternate realities, has been a wild start to the sixth season with the death of Archie Andrews (KJ Apa) in the premiere.

Last week, Rivervale claimed another victim when Toni Topaz (Vanessa Morgan) became the new La Llorona, the grudge-holding spirit in the town's lake drowning and killing babies. After La Llorona attacks Toni's son Anthony, Toni volunteers to trade places with the ghost in exchange for her baby boy's life. Anthony is now being cared for by Betty (Lili Reinhart), who lost her unborn baby to La Llorona.

Camila Mendes, Cole Sprouse, Mädchen Amick, Casey Cott, Charles Melton, Erinn Westbrook and Drew Ray Tanner also star in the series.

Shipka's appearance on Riverdale airs on Dec. 7 on The CW.