Legendary comic book creator Steve Ditko, who co-created Spider-Man and Doctor Strange with Stan Lee, has died aged 90, The Hollywood Reporter confirmed via the New York Police Department. A cause of death has not yet been announced.

Ditko was found dead in his Manhattan studio on June 29 and is believed to have died two days prior to his discovery. The famed Marvel Comics artist has no known survivors and is believed to never have married.

Ditko is responsible for imagining Spider-Man’s iconic red and blue costume as well as his trademark webshooters. With Lee, Ditko penned such enduring foes as the Green Goblin, Doctor Octopus, Sandman, and the Vulture, all of whom have appeared in numerous Spider-Man movies that have earned a lifetime total of nearly $5 billion worldwide.

After the pair teamed on Amazing Fantasy #15, Spider-Man’s first appearance, a newly-launched Marvel Comics spun the character off into his own book, The Amazing Spider-Man, which has published more than 800 issues since its first issue in 1963.

Lee and Ditko then conjured up psychedelic crime-fighter Doctor Stephen Strange in the pages of Strange Tales #110. Doctor Strange made his live-action big screen debut in the 2016 Marvel Studios blockbuster that proved a worldwide hit, with the character going on to reappear in Thor: Ragnarok and Avengers: Infinity War, where Spider-Man (Tom Holland) and Doctor Strange (Benedict Cumberbatch) famously teamed as they have so many times in the Marvel comic books.

Ditko continued on Amazing Spider-Man until issue #38 after a tenure that saw the creation of such classic characters as Aunt May and Uncle Ben, J. Jonah Jameson, Gwen Stacy, Norman and Harry Osborn, Betty Brant, Mysterio, Electro, and Kraven the Hunter.

On his time with Strange Tales, until issue #146 in 1966, Ditko brought to life such seminal Doctor Strange players as Dormammu, Clea, Nightmare, Wong, the Ancient One, and Karl Mordo, some of whom have made the jump into the Marvel Cinematic Universe.

Other Marvel characters co-created by Ditko include Hulk enemies Glenn Talbot and Samuel Sterns, a.k.a. the big-brained Leader.

Lee and Ditko famously split for reasons that were never entirely identified. In 2017, Lee recounted how the pair of comic book creators clashed over Lee’s decision to reveal the identity of Spider-Man’s arch enemy, the Green Goblin, as the father of Peter Parker’s best friend.

Ditko also co-created the Question for Charlton Comics and DC Comics superheroes Captain Atom, crime-fighting team Hawk and Dove, and the Creeper.