The latest episode of Invincible Season 4 took a sharp turn away from the Viltrumite war buildup, sending Mark Grayson on a surprising detour to the Underrealm. Episode 4, titled “Hurm,” dropped on Prime Video on March 25, 2026, and while it delivered a side quest to Hell, the final moments reminded everyone what’s really at stake.
The episode opened with Mark (voiced by Steven Yeun) still struggling with the weight of his recent actions. After killing Rus Livingston during the Sequid outbreak, he showed up at Art’s shop, trying to return his costume. The guilt was eating him alive as he confessed he nearly killed someone and would have if his brother Oliver hadn’t stopped him. Art, voiced by Mark Hamill, gave him a much-needed reality check.
“The fact that it’s eating you alive means you’re not him.”
Art’s words landed hard. He told Mark that if he truly believed he didn’t deserve the suit, he shouldn’t wear it. But when he remembered who he used to be, he would know when to put it back on.
Damien Darkblood Returns and Hell’s Power Struggle Unfolds
The episode then shifted to the Underrealm, where Damien Darkblood (voiced by Clancy Brown) made his return after being banished by Cecil in Season 1. The demon detective was in the middle of a brutal battle against Volcanikka (voiced by Indira Varma), a powerful fire-wielding villain who had taken control of Hell.
Volcanikka proved nearly impossible to kill, regenerating after every strike. She killed Damien’s sister Domina (voiced by Kate Mulgrew) in a horrifying moment, filling her body with magma before she exploded. With his forces destroyed, Damien had no choice but to summon reinforcements. He used the blood Mark had left at a crime scene to bring him to Hell.
When Mark arrived, he immediately tried to attack Satan (voiced by Bruce Campbell), thinking he was the enemy. Damien stopped him and explained that everything humanity thought about Hell was wrong. Satan wasn’t evil. Hell wasn’t a place of punishment. It was a prison created by demons to contain ancient creatures called the Viles, who would have destroyed Earth long ago.
Volcanikka planned to release the Viles onto the surface, which meant total annihilation. Mark agreed to help, but only if he didn’t have to hurt anyone.
The Bottomless Pit, Satan’s Crown, and Slayer
Mark and Damien jumped into a bottomless pit to retrieve Satan’s crown, the only thing that could restore his full power. The descent turned into one of the episode’s most talked-about moments, filled with absurdist humor. Mark kept questioning why Damien kept taking his helmet on and off. The answer? It helped him speak clearly. And because it “looks cool.”
At the bottom, they fought off Volcanikka’s forces, retrieved the crown, and returned to the surface. When Satan put on the crown, he transformed into his true, monstrous form. The moment was set to Slayer’s “Raining Blood,” creating what fans are calling one of the most metal sequences in the show’s history.
The final battle against Volcanikka saw Mark repeatedly beheading her until she retreated. But the Viles had already started emerging, forcing the demons to focus on containment. Mark returned to Earth, but not before Damien warned him that bigger threats were coming.
Eve’s Secret, Debbie’s News, and That Final Return
Back on Earth, the episode balanced the Hell storyline with meaningful character moments. Eve (voiced by Gillian Jacobs) told her friend William about her pregnancy, admitting she wasn’t ready to tell Mark yet. William tried to be supportive, joking that their baby would be the “hottest superbaby of all time.”
Debbie (voiced by Sandra Oh) told Mark and Oliver she wanted to move in with her boyfriend Paul and sell the family house. Oliver was supportive once Mark agreed.
Mark returned to Art’s shop and took back his old blue and yellow suit. It was a quiet moment, but it signaled a shift. He went to find Eve, ready to talk. They sat together, and Mark admitted he wasn’t okay. Eve was about to tell him about the pregnancy when two figures appeared in the sky.
Omni-Man (voiced by J.K. Simmons) and Allen the Alien (voiced by Seth Rogen) had returned to Earth. Nolan looked at his son and delivered the line that set up everything coming next:
“I’m sorry, Mark. We need you. The time for war is upon us.”
The episode’s post-credits scene showed Damien Darkblood back on Earth, standing over a city, hinting that the coming war would require his investigation skills once again.
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What This Episode Means for the Season
Episode 4 was a detour, and many reviews have pointed out how it slowed down the momentum built in the first three episodes. But it also gave Mark a rare moment to step away from his mounting guilt and process his emotions, even if it happened in Hell. The original story, created specifically for the show by Robert Kirkman, allowed the series to expand its mythology in a way the comics never did.
The final minutes, however, made it clear the show is shifting focus. With Nolan and Allen back, the Viltrumite War is now the central conflict. Mark will have to face his father, deal with Eve’s pregnancy, and prepare for the arrival of stronger Viltrumites like Thragg (voiced by Lee Pace).
Invincible Season 4 continues every Wednesday on Prime Video, with the next episode set to return to the main storyline. Episode 5 arrives on April 1, 2026.
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