The back story of Carnage and Venom is quite complex. Both originated from the symbiote species. Venom was the first to bond with a human host, and Carnage emerged as a more violent and unstable offshoot.
In the comics, the outcome of their battles varies. Sometimes Venom emerges victorious and kills Carnage, but there are also instances where Carnage escapes or the fight ends inconclusively.
The main characters are obviously Spiderman and Venom. Spiderman, Peter Parker, is the friendly neighborhood superhero with his spider - like powers. Venom is a complex character, a symbiote that bonds with a human host and has a grudge against Spiderman.
The key plot points include the first encounter between Spiderman and Venom in the graphic novel. It's a moment of shock for Spiderman as he realizes the power of this new enemy. Then there's the chase aspect, with Venom often chasing Spiderman through the city, causing chaos. And towards the end, there's the climax where Spiderman has to use his wits more than his strength to try and defeat Venom.
Well, it happened when the symbiote found Cletus Kasady. This combination of a powerful symbiote and a deranged mind gave birth to Carnage. The symbiote's influence amplified Kasady's evil tendencies, making him a truly terrifying force.