Who is the mystery symbiote joining Carnage in the follow-up event to Marvel's King in Black? The recently revealed Extreme Carnage storyline coming in July will see the typically villainous and serial-killing Carnage uniting several surviving symbiotes together to face "one of their greatest challenges yet" after Knull the Symbiote God's invasion of Earth. However, the identity of one of the symbiotes is "classified" and a total mystery. However, there is one symbiote host who seems perfect for this new assembly of symbiotes in the future of the Marvel Universe, just as soon as Knull's invasion has been dealt with by its heroes.
In the recent announcement from Marvel Comics, it's revealed that July's Extreme Carnage will be coming from writer Phillip Kennedy Johnson. Additionally, the announcement featured teaser artwork from artists Leinil Francis Yu and Sunny Gho, revealing the line-up of symbiotes that Carnage will unite, and thus far they're all family. This new alliance will consist of Carnage's five younger siblings known as the Life Foundation symbiotes: Lasher, Riot, Scream, Phage, and Agony. Furthermore, Carnage's son Toxin will be among their ranks as well, the 1000th symbiote in the lineage of Venom and Carnage.
However, the artwork has blacked out the eighth and final symbiote host as "classified", providing only a silhouette that's still pretty indiscernible. However, in keeping with the family motif, it would be a pretty dynamic addition if none other than Venom's son Dylan Brock and his symbiote Sleeper were revealed to be the secret host, seeing two more of his children joining whatever it is Carnage has planned. Dylan Brock and his unique abilities to control and manipulate other symbiotes at will would make him a valuable asset, while also potentially creating some interesting tensions. Perhaps Dylan joins to keep an eye on all of them?
While this is all pure speculation at the moment, it does make a certain amount of sense. Not only is Dylan technically part of the symbiote family as a human/symbiote hybrid, but he's been set up in King in Black to be a major player thanks to his powers over symbiotes, fighting side by side with Thor against Knull himself. As such, it seems doubtful that Dylan would just go back to being a normal kid again once the invasion is over. Additionally, Venom's final fate in the crossover is uncertain as the event is still ongoing, which means it's possible Dylan could step up and become the new Venom if the need arises in the future of the Marvel Universe (hence the silhouette to avoid spoiling his potential debut at the end of King in Black).
In any case, the identity of this mystery symbiote host won't be a mystery for long, though it's quite likely King in Black will provide more information as it nears its ultimate conclusion. Likewise, Extreme Carnage is going to be incredibly interesting, as the announcement from Marvel indicates that it will be reshaping the status quo for symbiotes going forward now that the entire world has recognized the threat they truly pose. It certainly seems as though that would be something Dylan Brock would want to a part of when Extreme Carnage comes to comic book store shelves this July from Marvel Comics.