Venom, or the Venom Symbiote, is a fictional character appearing in books published by Marvel Comics, usually those featuring Spider-Man. The character is a Symbiote, a sentient alien, with a gooey, almost liquid-like form that requires a host, usually human, to bond with for its survival, as with real world symbiotes, and to whom it endows enhanced powers. When the Venom Symbiote bonds with a human, that new dual-life form refers to itself as Venom.
The Symbiote's first known host was Spider-Man, who eventually separated himself from the creature when he discovered its true nature. The Symbiote went on to merge with other hosts, most notably Eddie Brock, its second and most infamous host, with whom it first became Venom and one of Spider-Man's archenemies. According to S.H.I.E.L.D., it is considered one of the greatest threats to humanity, alongside Magneto, Doctor Doom, and Red Skull.
Comics journalist and historian Mike Conroy writes of the character: "What started out as a replacement costume for Spider-Man turned into one of the Marvel web-slinger's greatest nightmares." Venom was ranked as the 22nd Greatest Comic Book Villain of All Time in IGN's list of the top 100 comic villains, and 33rd on Empire Magazine 's 50 Greatest Comic Book Characters.