Despite many doubts about separating the character created by Todd McFarlane from the Marvel canon (after all, the character’s identity is closely linked to Spider-Man), the first Venom managed to bring enough elements to Eddie Brock's (Tom Hardy) story independently, portraying him as a tortured antihero. The story follows Brock’s union with the alien symbiote (also voiced by Hardy) as part of a larger plot involving the Life Foundation corporation. In this way, the plot completely detaches itself from any references to the web-slinging superhero and gives Eddie his own fight to defend Earth.
The second installment of the trilogy expands the mythology of alien symbiotes by introducing the most iconic one (after Venom, of course): Carnage, the violent being housed inside the psychotic killer Cletus Kasady (Woody Harrelson). The film also introduces another villain from the Spider-Man universe, Frances Barrison/Shriek (Naomie Harris), and sets up the appearance of future characters more associated with symbiotes. However, the post-credits scene reveals that Eddie has been transported to the Marvel Cinematic Universe.
Venom: The Last Dance is the conclusion of the trilogy, culminating in the promise of an invasion of symbiotic aliens, with Eddie Brock as the only one capable of stopping it. The film will introduce the ultimate symbiote villain: Knull, the creator of the entire species.
It's worth noting Spider-Man: No Way Home as part of the saga, not because it contributes anything to the narrative itself, but because Eddie Brock appears in it, technically, though it’s a tiny cameo that leads nowhere. The post-credits scene shows Eddie stranded in Mexico after appearing in another universe, only to be returned to his original place by Doctor Strange’s magic. His visit to this corner of the multiverse doesn’t affect anything, except leaving behind a fragment of the Venom symbiote whose fate is, so far, unknown.