Comic artist Paul Ryan, known for his work on The Phantom in addition to numerous projects for Marvel and DC, has passed away at the age of 66. According to Bleeding Cool, Ryan’s cousin Chad Callanan confirmed his passing on Facebook.

“Chances are you were touched by him in your lifetime as he was the cartoonist for some of the most well-known and beloved characters in the world. From Spider-Man, Thor, Iron Man, The Phantom to the Fantastic Four, most of which made it to the big screen and Hollywood. He was a true giant and artist, who achieved more success in his short life than any one of us would ever know in ten lifetimes,” Callanan posted. “But he was also my friend and that was good enough.”

After growing up a fan of comics, having watched shows as The Adventures of Superman and reading various Silver Age classics throughout the 1960s, Ryan was prompted to create his first story, Breed. It was created in response to a general “open audition” offer from Charlton Comics. Eventually, Ryan’s career truly got started after Marvel artist Bob Layton hired him as an assistant doing backgrounds.

Ryan spent a year doing backgrounds at Marvel before getting his own assignments, starting with The Thing and then moving on to pencils on titles like Iron Man and Squadron Supreme. He later worked on Avengers and on Fantastic Four, and on the latter was known for his significantly long run. He trailed only Jack Kirby and John Byrne in number of issues drawn on Fantastic Four.

In the mid-’90s, he left Marvel to work for DC, where he was the artist on Superman: The Man of Tomorrow and The Flash. He also penciled various Batman and other Superman titles. Ryan began working on The Phantom comic strip in the mid-2000s, and continued on and off on it for a number of years afterwords.