Originally one of an army of Symbiote Dragons brought by the symbiote god Knull during his invasion of Earth, this symbiote was targeted by Iron Man when the Armored Avenger was attempting to collect a symbiote to save the life of Eddie Brock, who had been near-fatally injured by Knull after being stripped off the Venom symbiote. Using a dose of the techno-organic virus Extremis, Iron Man attempted to rewrite the symbiote's DNA to sever its connection from Knull's Hive. In the process of subduing the symbiote, the creature infused itself into Iron Man's armor. Iron Man would then attempt to bond Eddie Brock to a portion of the symbiote, but the gambit failed since the symbiote remained connected to Knull, and Brock died.
Eddie's son Dylan Brock was able to sever the symbiote's connection to the Hive-Mind, granting Iron Man full control over it. When Knull, wounded by Thor Odinson, ordered the symbiote-possessed Celestials to raze Manhattan, Iron Man used his symbiote to hijack control of one of them. Stark returned to a version of his armor without a symbiote following Knull's defeat, and placed the Extremis-augmented symbiote-armor, which he dubbed the "Extrembiote," into storage in his lab. Stark later showed it to Flash Thompson, who warned him that he shouldn't treat it as a mere suit of armor and wouldn't be able to control it forever, though Stark disregarded this, citing Flash's apparent ability to control his own symbiote.
Wanting to test the Extrembiote's capabilities as well as help out in the fight against Carnage, Tony Stark bonded to it and used it to separate Arthur Krane from the Carnage symbiote. However, Cletus' codex called out to the Extrembiote from within the Hive-Mind, mocking Tony for thinking he could control it and causing it to break his arms and several ribs. Carnage merged with the Extrembiote but was stopped from killing Tony by Agent Anti-Venom, transforming into a symbiote-dragon and flying away while gloating that he was victorious. At some point afterwards, Cletus' codex and the Carnage symbiote had a falling out and he expelled it from the Extrembiote, opting to keep it as his new avatar.
Cyborg Symbiote Physiology: As a creation of Knull, the Extrembiote possessed immense powers like other Symbiote Dragons. Following its infusion with the Extremis virus and merging with a suit of Iron Man's Model 70 armor, the Extrembiote also developed new powers.
- Constituent-Matter Manipulation Like other symbiotes, the Extrembiote is capable of manifesting tendrils from its biomass, using them to attack prey.
- Cleansing Beam: As a result of its mutation with Extremis and its merging to the Iron Man Armor, the Extrembiote gained the ability to project repulsor blasts capable of cleansing Knull's corruption off one of his victims.
- Possession: Iron Man managed to use the Extrembiote to override Knull's symbiotic possession of a Celestial, taking full possession of the cosmic being himself.
- Shapeshifting: While it primarily resembled a black-and-yellow Gigeresque version of Iron Man's Model 70 armor, the Extrembiote was capable of returning to its draconic form at its host's command.
- When it bonded to Tony Stark, the text on his armor's HUD changed to the symbiote language and Knull's spiral emblem appeared on Tony's forehead.
- 8 appearance(s) of Extrembiote (Earth-616)
- 27 image(s) of Extrembiote (Earth-616)
- 1 item(s) used/owned by Extrembiote (Earth-616)