At the end of Venom: Let There Be Carnage, Eddie Brock (played by Tom Hardy) and Venom are sitting in their apartment, discussing their latest adventure. Suddenly, Venom’s eyes turn blue, and he reveals that he’s not actually the Venom that Eddie knows, but rather an ancient symbiote called “Knull,” who was thought to have been destroyed long ago.
The reason for Venom’s eyes turning blue is related to the backstory of the symbiotes in the Marvel Comics universe. Knull is the god of the symbiotes and was the first symbiote to ever exist. He has the ability to control all symbiotes and is considered to be incredibly powerful. In the comics, Knull has blue eyes, and it seems that this detail was carried over to the movie to indicate the change in identity from Venom to Knull.
In the movie, it’s revealed that Knull has been manipulating Eddie and Venom all along, using them as a way to escape his prison and take over the Earth. Venom is initially resistant to Knull’s control, but eventually succumbs to his influence, leading to the blue-eyed reveal at the end of the movie.
It’s worth noting that the blue-eyed Venom/Knull is likely setting up the events of future movies in the Sony Pictures Universe of Marvel Characters. In the comics, Knull is a major villain who has crossed paths with many of Marvel’s heroes, including Spider-Man and the Avengers. It’s possible that we’ll see Knull face off against some of these characters in future movies, and the blue-eyed Venom/Knull is just the beginning of his reign of terror.
Overall, the reason for Venom’s eyes turning blue at the end of Venom: Let There Be Carnage is a nod to the character’s comic book roots and sets up potential future storylines in the Sony Pictures Universe of Marvel Characters.