The adult animated superhero series Invincible continues to surprise audiences with its fourth season on Prime Video. Episode 4, titled “Hurm,” which released on March 25, 2026, took viewers on an unexpected trip to the Underrealm (Hell) for a demonic war storyline. While Steven Yeun returns as the voice of Mark Grayson, the episode features a collection of new guest voices and one notable recast that has fans talking. This episode focuses heavily on the battle between demonic forces and a lava-wielding antagonist, bringing in actors from franchises like Game of Thrones, Star Trek, and The Evil Dead.
Satan Makes His Full Debut Voiced by a Horror Legend
After being teased in the Season 3 finale, the character known as Satan (or The Great Beast) officially steps into the spotlight in Episode 4. Voicing this powerful demon is Bruce Campbell, the cult icon famous for playing Ash Williams in The Evil Dead franchise. Campbell’s casting is a perfect fit given his long history with horror and genre storytelling.
In the episode, Satan is introduced in a weakened state, having lost his crown to the antagonist Volcanikka. Mark Grayson (Steven Yeun) must help Damien Darkblood retrieve the crown from a bottomless pit to restore Satan’s power. Once the crown is returned, Satan transforms into his true monstrous form, set to the heavy metal music of Slayer’s “Raining Blood,” creating a memorable sequence for fans.
Campbell’s performance brings a mix of authority and dry humor to the character. He previously appeared in the series uncredited in Season 3 as a demon, but this marks his first major role in the show.
William Clockwell Recast: Brandon Scott Jones Takes Over
One of the most talked-about changes in Episode 4 is the voice of William Clockwell, Mark’s best friend. The character, who had been absent for most of Season 4, returns for a scene with Atom Eve (Gillian Jacobs) where she discusses her pregnancy. Longtime viewers will notice a different voice, as Brandon Scott Jones has taken over the role.
Jones is an actor and comedian known for playing Isaac Higgintoot in the CBS sitcom Ghosts and for his recurring role in The Good Place. He replaces Andrew Rannells, who had voiced William since Season 1. As of the episode’s release, neither series creator Robert Kirkman nor Prime Video has provided an official explanation for the recasting, though scheduling conflicts are often the reason for such changes. Some fans on social media have noted the change, but Jones’ performance stays true to William’s familiar humor and personality.
Volcanikka and Domina: New Faces in the Underrealm
Episode 4 introduces two significant new characters to the Invincible universe, both voiced by acclaimed actresses.
Indira Varma voices Volcanikka, the episode’s main antagonist. Volcanikka is a powerful elemental warrior who controls magma and commands an army of Magmanites. She has taken control of Hell and plans to release ancient creatures called the Viles onto Earth’s surface. Varma is a British actress best known for playing Ellaria Sand in Game of Thrones and Niobe in Rome. She also recently voiced The Bride in the DCU animated series Creature Commandos.
Kate Mulgrew voices Domina Darkblood, the sister of Damien Darkblood. Domina is an original character created specifically for the animated series and does not appear in the original Robert Kirkman comics. Mulgrew is a fan-favorite actress known for playing Captain Kathryn Janeway in Star Trek: Voyager and Red in Orange Is the New Black. Her performance brings theatrical energy to the demonic family drama unfolding in Hell.
Returning Voices: Clancy Brown, Gillian Jacobs, and More
The episode also features several returning voice actors who continue their roles from previous seasons.
Clancy Brown returns as Damien Darkblood, the demon detective first introduced in Season 1 investigating Omni-Man’s crimes. Brown, known for voicing Mr. Krabs in SpongeBob SquarePants and for his roles in The Shawshank Redemption and Highlander, also voices the ancient Egyptian entity Ka-Hor in this episode. His performance anchors the Underrealm storyline, providing weight to the demonic conflict.
Gillian Jacobs continues as Atom Eve (Samantha Eve Wilkins), Mark’s girlfriend. In Episode 4, Eve shares her pregnancy news with William, expressing her uncertainty about becoming a parent while Mark remains unaware. Jacobs is widely recognized for her role as Britta in Community.
Sandra Oh voices Debbie Grayson, Mark’s mother. In this episode, Debbie tells Mark and Oliver that she plans to move in with her boyfriend Paul and sell the family house. Oh is known for her work on Grey’s Anatomy and Killing Eve.
J.K. Simmons appears briefly as Omni-Man (Nolan Grayson), whose blood is used in a summoning ritual, and he appears in the final moments of the episode alongside Allen the Alien. Simmons is an Oscar-winning actor known for Whiplash and voicing J. Jonah Jameson in Spider-Man movies.
Seth Rogen voices Allen the Alien, who returns to Earth with Omni-Man in the episode’s closing scene, setting up the Viltrumite War storyline.
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Additional Voice Cast and Episode Details
Other voice actors contributing to Episode 4 include Vanessa Marshall (Star Wars: The Bad Batch) and Andrew Morgado (Archer) in supporting roles. Grey DeLisle also provides additional voices as she has throughout the series.
The episode was written by series creator Robert Kirkman himself, and it expands the mythology of the Underrealm in ways not found in the original comics.
Invincible Season 4 Episode 4 is now streaming on Prime Video. New episodes release every Wednesday, with Episode 5 scheduled for April 1, 2026. The season consists of eight episodes total, with the finale airing on April 22, 2026.
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