WARNING: The following contains spoilers for Venom #32, by Donny Cates, Iban Coello, Jesus Aburtov, and VC's Clayton Cowles, on sale now.
In King in Black #1, the god of the symbiotes, Knull, has invaded Earth. He defeated Earth's heroes in record time, and he ripped the Venom symbiote off of Eddie Brock and dropped him down the side of a building to his death.
Venom #31 and King in Black #2 by Donny Cates and Ryan Stegman, showed how Eddie hit the ground, and how he managed to cling to life until Tony Stark attempted to bond him with a symbiote dragon, a process that has left Eddie, for all intents and purposes, dead. However, Eddie lives on, or at least a part of him does. In Venom #32, Eddie is clinging on to life in the hive-mind of the symbiotes, and he comes across an old friend in Rex Strickland.
Rex Strickland first appeared in the first volume of 2018's Venom series by Donny Cates and Ryan Stegman. Rex was originally a soldier who took part in the Vietnam War, where he fought as part of a special team of super-soldiers bonded with symbiotes. While Rex was eventually killed, his symbiote kept his appearance and assumed his identity thanks to the codex that was now a part of the hive-mind. Years later, Rex then approached Venom, and recruited him so that Eddie could help him rescue the other symbiotes that fought alongside Rex during the war. Rex and Eddie spent a brief amount of time together, but he still managed to become a mentor to him. Rex taught him how to better understand his symbiote, and about the larger history of the Klyntar. Unfortunately, Rex was killed during the battle with the Grendel, and Eddie has been more or less on his own in this epic battle ever since before their reunion.
The story picks up where Venom #31 and King in Black #2 left off, with Eddie landing on a car after falling from a building, and with him dying after the attempt to bond him with a symbiote dragon. But while Eddie's physical body is dying, he is watching all of it from the outside. Now that Knull has reclaimed the Venom symbiote, Eddie's consciousness, which is contained inside a codex, is now part of the hive-mind. The hive-mind is a sort of parallel dimension, a purgatory-like reality where Eddie can see the world, but can't interact with it. There, he is rescued by the symbiote of Rex Strickland who, unlike all the other symbiotes, is free of Knull's control.
Rex explains that both of them are just the memories of their hosts, codices that are now living inside the hive-mind. But since both of them have experienced living with a symbiote, they are not under the thrall of the hive yet. They are still themselves, and they can fight back from this side.
Eddie Brock may have died in King in Black #2, but he isn't out of the fight just yet. Now, his codex is awake inside the hive-mind, and he plans on freeing the Venom symbiote from Knull's control. If he does that, then perhaps Venom, like Rex, will be able to assume Eddie's identity, allowing him to live on in the Marvel Universe.