Alien costume and Venom

Spider-Man gets a new black costume in Secret Wars #8.
Art by Mike Zeck.The alien costume, also known as the Black Suit, first made its appearance in sketches found in a Marvel magazine titled Marvel Age #12. These early sketches had Spider-Man in a black costume with a red spider-symbol instead of the version with the white symbol that would later be used. The first comic book appearances of the suit occurred in May of 1984 in Marvel Team-Up #141, Amazing Spider-Man #252, and Spectacular Spider-Man #90.

In these issues there was an abrupt time shift from the issues a month earlier. Spider-Man was now on Earth shortly after the events of the Secret Wars limited series had taken place even though the twelve issue Secret Wars series had just started that month. It would be months before the change to the new costume would be explained. In the Secret Wars limited series, Spider-Man is taken to an alien planet, where he participates in a battle between Earth's greatest heroes and villains. When his suit is destroyed in the fight, Peter sets out to make himself a new one and comes across a machine which conjures him a black suit that responds to his thoughts, greatly enhances his powers, provides him with its own supply of web-fluid, and can change its appearance at his command.

After he returns to Earth, however, Peter discovers that the costume is actually an alien symbiote bent on permanently bonding with its host. Peter eventually rejects and defeats the symbiote, but it merges with reporter Eddie Brock, becoming the villain known as Venom. Brock is imprisoned and removed from his symbiote but then escapes from prison when the symbiote returns. His cell-mate, Cletus Kasady (a serial killer), merges with an infant symbiote that Venom left behind, thus becoming another villain, Carnage.