Helstrom was a Hulu web series set within the Marvel Cinematic Universe created by Paul Zbyszewski and centered on the Marvel Comics characters Daimon and Satana Hellstrom, siblings who have a complicated dynamic as they hunt down demons using with their attitude and skills."
- Tom Austen as Daimon Helstrom / Basar: A professor of ethics who moonlights as a demon hunter, Daimon is determined to root out demons as they arise, and will not stop until they're vanquished.
- Noah Hupp as Young Daimon Helstrom
- Sydney Lemmon as Ana Helstrom: By day, Ana runs a successful auction house and suffers no fools, but her true interest lies in protect the innocent from the forces of evil. Ana is driven to rid the world of demons.
- Erica Tremblay as Young Ana Helstrom
- Elizabeth Marvel as Victoria Helstrom / Kthara: Victoria has been institutionalised for twenty years. While she struggles to be herself, she hopes to repair her relationship with her children.
- Robert Wisdom as Caretaker: Caretaker is a guardian of knowledge of the occult. He uses his knowledge and his relationship with Ana to help keep demonic forces at bay.
- June Carryl as Dr. Louise Hastings: A psychologist with a strong faith but an open mind, Hastings is head of the psychiatric hospital where Victoria is being monitored. She has watched over the Helstrom family for years, caring for them as best she can.
- Ariana Guerra as Gabriella Rosetti: Gabriella arrives from the Vatican to help Daimon hunt down demons. She wants to save everyone she can, including Daimon. 
- Alain Uy as Chris Yen: Yen is Ana's business partner and her closest friend -- some would say surrogate brother. He carries out the bulk of the auction house's responsibilities and assists Ana with whatever she needs. 
- Daniel Cudmore as Keith Spivey / Basar: A nurse at a hospital where Victoria Helstrom is being held in.
- Shayn Walker as Ellis: A security guard.
- Deborah Van Valkenburgh as Esther Smith: The leader of Blood.
- Zachary S. Williams as Bryce / Magoth: A student at a school where Daimon Helstrom works in.
- David Meunier as Finn Miller / Magoth: A member of Blood.
- Trevor Roberts as Father Joshua Crow / Raum: A priest.
- Hamza Fouad as Derrick Jackson: A police officer and Chris Yen's boyfriend.
- Fiona Dourif as Kthara: A demon who possessed Victoria.
- Grace Sunar as Lily: A girl who seems to be Kthara's true form and name.
- Mitch Pileggi as Marduk Helstrom: A powerful demon and serial killer.
- Jen Landon as Dr. Katherine Reynolds: A doctor who aids Daimon.
- Sandy Robson as Alex Tilden / Magoth: A truck driver.
- Kyle Warren as Cameron Tate: A man who is concerned about his brother's death.
- Samantha Sloyan as Jolene Spivey: Keith's wife.
- Tom Everett as Archbishop Terrazi: A priest who worked for Blood.
- Tarun Keram as Lee: A member of Blood.
- Jesse James Baldwin as Archer Cavallo: A boy who fakes being a demon.
- Eric Gustaffson as Edward Tate: Cameron's brother who is a criminal and is murdered by Ana.
- Todd Thomson as Mr. Cavallo: A man who seeks help from Daimon and Gabriella after his son is appeared to be possessed by a demon.
- Jessie Fraser as Mrs. Cavallo: Cavllo's wife.
- Shane Leydon as Hock: A patient who helped Kthara.
- Mig Macario as Liddle: A patient who helped Kthara.
- Hiro Kanagawa as Father Sean Okamoto: A priest.
- Camille Sullivan as Aubree Richards and Zoe Richards: The twins who were affected by Marduk.
- Brody Romhanyi as Keeper: An entity who keeps demons at bay.
|No.||Title||Directed by||Written by||Original air date|
|1||"Mother's Little Helpers"||Daina Reid||Paul Zbyszewski||October 16, 2020|
|Daimon Helstrom investigates a possessed young boy in Oregon. Meanwhile in San Francisco, Ana Helstrom stages an auction to expose a criminal. Disturbing events at St. Teresa's cause concern as the siblings' estranged Mother remains hospitalized.|
|2||"Viaticum"||Anders Engstrom||Blair Butler||October 16, 2020|
|A horrific accident leads Daimon and Gabriella fighting to save a man's soul, while a dark force attempts to stop them. Yen's relationship with his work takes a dark turn towards obsession, and a discovery leads Ana back to St. Teresa's.|
|3||"The One Who Got Away"||Michael Offer||Marcus Dalzine||October 16, 2020|
|Daimon and Ana learn more about the destruction their father left in the wake. With Gabriella, they pay a visit to a potential victim and find themselves in deeper than they ever could have imagined. Hastings shocks Caretaker with a stunning revelation.|
|4||"Containment"||Amanda Row||Shelia Wilson||October 16, 2020|
|A demonic enemy brings together an unusual group. Daimon and Ana travel to San Francisco in search of Yen and an artifact that may help defeat the enemy. Ana tells Daimon about her extracurricular activities, and Gabriella's faith is attacked.|
|5||"Committedd"||Jovanka Vuckovic||Ian Sobel & Matt Morgan||October 16, 2020|
|Things are not what they seem as Mother's health sharply declines. As Ana searches for Yen, Gabriella offers counsel to a student struggling to understand how demons live among us. Daimon makes a discovery that is truly a matter of life and death.|
|6||"Leviathan"||Sanford Bookstaver||Amanda Segal||October 16, 2020|
|A dark force creates a melee forcing Hastings and Ana to work together. Daimon and Gabriella discover the events of the Blood Hotel are connected. The demon's identity is revealed, shaking Ana and Daimon to their core. Yen gets the upper hand.|
|7||"Scars"||Bill Roe||Mark Leitner||October 16, 2020|
|With a powerful demon looking for a new host and Ana struggling to control her dark urges, Daimon is offered a proposition from The Blood. Caretaker finds himself in hot water, and Dr. Hastings rattles Daimon with new revelations about his past.|
|8||"Underneath"||Cherie Nowlan||Maggie Bandur||October 16, 2020|
|Relationships deepen as stakes increase. To save a life, Hastings and Ana must do the unthinkable. Gabriella and Daimon journey to his old childhood home in search of an old relic. A mother loses a son but gains an heir.|
|9||"Vessels"||Kevin Tancharoen||Ian Sobel & Matt Morgan||October 16, 2020|
|Daimon and Gabriella find themselves in disturbing new territory. Ana has to make a decision that will change the course of the siblings' lives in irreversible ways. Victoria tries to make amends but she may be too late.|
|10||"Hell Storm"||Jim O'Hanlon||Paul Zbyszewski||October 16, 2020|
|Ana and Daimon fight to save a soul but only Yen can be victorious. Gabriella's newfound perspective challenges Daimon's beliefs, creating rifts amongst the groups. Victoria unites with Daimon and Ana, but their victory comes at cost.|
- Helstrom was originally planned to be the first in Marvel Television's Adventure Into Fear. However, Adventure into Fear was cancelled in October 2019, while development for Helstrom was transfered to Marvel Studios after Marvel Television was folded into that company, causing all of Marvel Television's in-development series to be cancelled.
- Because of Adventure into Fear being cancelled and Marvel Television shutting down, this is the very final Marvel Studios series to have a looser connection with the MCU, as well as the final Marvel Studios series aimed at an adult audience. Following the end of this series's only season, future MCU series will be more strongly connected to the MCU films, and they will all be aimed at a family audience (due to all of them airing on Disney+).
- This series is the only new MCU production released in 2020.
- "Marvel’s Helstrom TV series reveals its cast". Den of Geek (October 8, 2019).
- Goldberg, Lesley (December 8, 2019). Marvel TV Division Folded Into Studio Unit, Layoffs Expected. The Hollywood Reporter. Archived from the original on December 11, 2019. Retrieved on December 11, 2019.
- ‘Helstrom’ Canceled at Hulu After One Season, Ending Jeph Loeb Era of Live-Action Marvel Television