Appearing in 1st story
- Iron Man (Tony Stark) (Bonded to a symbiote) (Main story and flashback)
- Doctor Doom (Victor von Doom)
- "Santa Claus" (Mike Dunwoody) (Controlled by Knull) (First appearance)
- "Santa Claus"' Reindeer (Only appearance; dies)
- Howard Stark (Only in flashback)
- Santa Claus (Mentioned)
- Eddie Brock (Mentioned) (Deceased)
- Symbiote Hive
- Numerous unnamed Symbiotes
- God (Yahweh) (Invoked)
- Knull (Mentioned)
- Captain America (Steve Rogers) (Referenced)
- Ms. Marvel (Kamala Khan) (Referenced)
- The Thing (Ben Grimm) (Referenced)
- Cyclops (Scott Summers) (Referenced)
- Dasher (Mentioned)
- Dancer (Mentioned)
- Krampus (Mentioned)
- B.O.S.S. (Voice)
- Snow Globe Holiday Decoration Supply (Mentioned)
Races and Species:
- Earth (Main story and flashback)
- United States of America (Main story and flashback)
- Iron Man Armor Model 70 (Assimilated by a symbiote)
- Iron Man's Symbiote
- Doctor Doom's Armor
- "Santa Claus"' Symbiote (Only appearance; dies)
- Extremis (Mentioned)
- Mike Dunwoody's Sleigh (Destruction)
Synopsis for 1st story
In a flashback, Howard Stark gifts his young son Tony the Johnson & Bernstein Building in Manhattan for Christmas, Tony isn't enthusiastic since he doesn't believe in Santa Claus despite Howard's attempt to make him play along. In the present, Manhattan is overrun by symbiote tendrils due to Knull's invasion. Tony, whose armor has been bonded with an Extremis-modified symbiote, is mourning the death of Eddie Brock that he accidentally caused in an attempt to save his life. He is approached by Doctor Doom, and both are then distracted by what appears to be Santa Claus flying in the sky, although corrupted by Knull.
Iron Man and Doom engage Santa as he tries to kill them with his reindeer and explosive presents. Tony manages to use his armor's new powers to take control of Santa's sleigh and flip it over, plunging him into the streets below. Santa survives and, as he tries to attack Iron Man with symbiote tendrils, Tony attacks him with a repulsor blast from his new armor. When the two attacks meet, a massive explosion cleanses Knull's corruption off Santa. He acknowledges both Tony and Victor and walks away. Tony finds a driver's license that fell off Santa that identifies him as a man named Mike Dunwoody who owns a Christmas decoration supply store. Doom reveals that he approached Tony due to his new armor, and wants to extrapolate its modifications into himself to defeat Knull, but Tony refuses. Doom ponders about what just happened, and Tony flies off, leaving him deliberating if maybe the man they encountered was actually Santa.
A long time ago, a young Tony Stark uncovers his eyes at his father's requests, who wishes the kid merry Christmas. They are both standing on a rooftop in Manhattan, and Howard is gesturing to a skyscraper behind them. When Tony points out that it's a building, Howard proudly clarifies that it's the Johnson & Bernstein Building, prime Manhattan real estate. After Tony unenthusiastically thanks him, Howard tries to make Tony play along that Santa Claus got it for him, but Tony tells him that he knows how it works. Howard warns Tony that if he wants to let go of all the magic in the world, it will turn cold and gray.
In an inner monologue, Tony recalls Howard's final words. It's the present, and Manhattan is covered in symbiote tendrils due to Knull's invasion. Tony thinks that maybe his father was right in ways he didn't realize and recalls that Eddie Brock is cold and gray too, after a failed attempt at bonding him to a symbiote sliver killed him, and blames himself for it. Tony is wearing his armor, which is bonded to an Extremis-mutated symbiote. From a rooftop, he is looking over at the Johnson & Bernstein Building, which is also covered in symbiote tendrils. It brings to Tony's mind that he sold it when he was thirteen years old and made a six million dollar profit. He recalls that Howard told him he was proud of him, and ponders if Howard had gotten a look at Iron Man as a kid, and stresses that that would have been magic. As he sits on the rooftop ledge looking discouraged, Tony contemplates that his heroic efforts these days end up being the opposite, and brings up Eddie Brock again. Doctor Doom appears behind Tony, posing the question whether Stark would mourn him as he is mourning Eddie Brock. Tony tells Doom that it depends, and ask him if in this scenario he killed Victor while trying to save him. Doom points out that saving him is what many of Tony's colleagues constantly waste their time trying to do. Tony replies that maybe they should give up on that. Victor expresses that Stark has never much been one to give up. Tony suddenly shifts his attention to the sky, noticing what appears to be the silhouette of a sleigh far in the distance. As he stands up, Tony and Doom discuss the possibility that it's Santa Claus, with Doom denying it vehemently and dismissing him as folklore. The figure comes closer, and a group of reindeer pulling the vehicle become visible. After exclaiming in a dumbfounded manner that Santa is real, Tony interrupts himself to notice that Santa Claus is corrupted by Knull, with tendrils covering his sleigh and his body. He is standing on the sleigh, singing a deranged and violent version of a Christmas carol.
Despite Doom's insistence that it can't be Santa Claus, Iron Man convinces him to engage him before he hurts someone, and both take flight. In his monologue, Tony thinks to himself how Knull it wasn't enough to take control of other superheroes, but he also had to ruin the holidays. Doom hovers in the path of the sleigh, and as soon as Tony tries to warn him, the reindeer disgorge symbiote goo into Doom. An energy field surrounding Doom disintegrates the substance while he uses his gauntlet's blasts to blast the two animals. As Tony wonders which of Santa's two reindeer were those, Doom begins to tell him about Latveria's own holiday figure, a singing ghost made of ox hair. He is interrupted by Santa, who hurls a present at his two opponents while singing. The box explodes, sending Iron Man and Doom crashing into a building. As they recover from the blast, Tony laments that after killing Eddie Brock he is going to kill Santa. Victor dismisses Brock as weak an addict to symbiosis. When Tony points out that he stopped terrible things, Doom tells him that Eddie was a victim, and that to pity them is to further disgrace them. Iron Man asks Doom why is he here, and he replies that he wants to tell Tony that Brock was worth the sacrifice. Tony asks why, pointing out that Knull is still out there and Eddie was their only hope. Doom tells Tony that Eddie's death resulted in him, perplexing Stark. Tony's attention shifts when he notices Santa still flying in the sky.
Iron Man grabs onto Santa's sleigh and the symbiote tendrils of his armor latch into it and begin expanding. As Tony takes control of the sleigh, Victor blasts the remaining reindeer. Doom explains in delight how Tony's armor is a perfect synthesis of Extremis combined with the limitless power of Knull's symbiote realm. Tony flips over the sleigh, making Santa fall. Both he and Doom attempt to reach him before he falls on the ground, but they fail and Santa plunges into a car. After the symbiotic material of Tony's suit returns to him and Doom points out the brilliance of it, Santa emerges from the wreckage cursing in anger. Tony attempts to talk to him and asks him if he truly is Santa. Doom tells him that even if he is, he must be destroyed due to Knull's corruption. When Santa asks Tony in anger if he doesn't believe in him, Stark explains that he wants to know that the world isn't just cold and gray. He elaborates that he doesn't want to believe it's just death and sadness and failure, because if it isn't that means there is a small chance to come back from Knull's invasion. Santa tells him that there is no return, and disgorges tendrils out of his mouth and eyes while laughing maniacally. Iron Man counteracts with repulsor blasts of purple and black energy, which cause a massive explosion when they meet Santa's attack. Doom shields himself with debris exclaiming the end of Santa's reign.
The explosion leaves a radius of destruction in the buildings nearby and symbiote substance scorched into the ground. Iron Man and Doctor Doom emerge from the debris. Tony asks what happened, and Doom tells him that he killed Santa. Tony laments until Victor directs his attention to Santa emerging from the destruction as well, with no signal of Knull's possession. They both attend to him. He turns to Iron Man, calling him Tony, and tells him he is a good boy. He shifts to Doom and, referring him as Victor, calls him one of the naughtiest to have ever lived. As he walks away adjusting his hat, Santa is asked by Doom if he is the rightful ruler of the North Pole. Doom also comments that they killed his reindeer, and states he must find a new method of transport. Santa tells him that he will find his way home. Iron Man crouches to grab a driver's license that identifies him as Mike Dunwoody. He asks B.O.S.S. to scan it, and the A.I. discloses that he is resident of Paramus, New Jersey, and the owner of Snow Globe Holiday Decoration Supply. Doom points out that Tony was able to reverse the effects of Knull's assimilation. Tony mentions that even in this condition, he is no match for Knull. Victor assures him that Tony's amalgamation could be extrapolated to something that could be. Tony deduces that that's the reason Victor paid him a visit, because he wants his armor, and shoots down the idea. As Tony and Victor walk away from the wreckage, Doom mentions that he is perplexed that Mike Dunwoody referred to both of them by their real names. Tony brings up that neither of them have a secret identity. Victor then observes that Mike quantified the sum moral value of each one's respective deeds. Tony interjects that it's also not hard, and reassures Victor that its okay if he wants to believe that Mike was Santa. Victor repudiates Tony's comment, arguing that he is only conducting an investigation of what just occurred. Tony sarcastically comments that Santa Claus existing is out of the realm of possibility in a world currently overrun by symbiotes. Tony flies off, telling Victor to not let go of all the magic in the world. Doom is left deliberating if Santa could be a Sorcerer Supreme.
Iron Man has risked everything to save Eddie Brock, but now he's left with nothing but guilt. As longtime 'frenemy' Doctor Doom shows up with both counseling words and ulterior motives, they'll be forced to battle an all-too-familiar specter of the holiday season -- albeit one now twisted and controlled by the recent invasion of Earth by the symbiote homeworld. As Iron Man and Doom fight as temporary allies, their unexpected encounter both with each other and a horrifying inversion of yuletide joy may ultimately reveal to them the true meaning of Knull-mas.
- This issue takes place after King in Black #2. It's also in that issue that Iron Man bonds his armor to an Extremis-modified symbiote and then attempts to save Eddie Brock's life but fails.
- The design of the symbiote-infused Iron Man Armor Model 70 as it appears in this issue is based on the Iron Man Armor MK VII from the Marvel Cinematic Universe (except colored black and with symbiote tendrils). It resembles this suit to varying degrees throughout the comic and more closely starting in page 11. In the first panel of page 4 it also resembles the Bleeding Edge Armor. This contrasts the suit's design in the main King in Black comics, in which the suit more closely resembles its original design.
- When taking flight to engage Santa Claus, Iron Man mentions Captain America, Ms. Marvel, The Thing and Cyclops as victims of Knull. Among other heroes, they were all taken over by Knull in King in Black #2.
- Iron Man #254 served as one of the inspirations for this issue's story.
- One of the Christmas carols Santa Claus references in this issue is "Silent Night". The lines "Silent night! Holy night!/All is calm, all is bright" are changed to "Violent night, no moonlight.../All is Knull, all is blight."