NEW YORK, NY.- John Cassaday, an award-winning comic book artist best known for his runs on Planetary, a series he helped create about a trio of adventurers investigating strange events, and Astonishing X-Men, on which his work offered readers a new entry point to a decades-old franchise, died Sept. 9 in New York City. He was 52.

Tara A. Martinez, his partner, said he died of cardiac arrest in a hospital.

In a medium known for its often fantastical scenarios, Cassaday’s drawings conveyed a sense of realism. Nowhere was that more evident than in his work on Planetary, which he created with writer Warren Ellis. His work on that series “rightfully put him on the map,” Mark Waid, a comic book editor and writer, wrote on Facebook.

Writing in his newsletter after Cassaday died, Ellis recalled one of the first times he met with him about working together on Planetary, which began in 1999.

“John said he’d love to try a monthly series, but hated the idea of having to draw the same thing every issue,” Ellis wrote. He rarely did: Within the first year of the series, Cassaday drew versions of pulp heroes like Doc Savage, an island of monsters reminiscent of Godzilla, the ghost of a Chinese police officer who had been wrongfully killed, and a doppelgänger of Marilyn Monroe who was subjected to scientific experiments by the government.

Perhaps the easiest character to draw was the Drummer, one of the investigators, whom Cassaday modeled on himself.

The covers, drawn and designed by Cassaday, were like movie posters, with the Planetary logo reimagined each time.

Cassaday received an Eisner Award, the comic book industry equivalent of the Oscar, for best penciler/inker in 2004. He tied for the award with Frank Quitely in 2005 and won it again in 2006, for Planetary and Astonishing X-Men. The writer of that title was Joss Whedon, the creator of “Buffy the Vampire Slayer” and the writer and director of several Marvel movies.

“There are basically three people that I would count as the easiest collaborations, the most natural, the best I’ve ever worked with,” Whedon said in an interview. “One is an actor, one is an editor, and one is Johnny. He knew so much of what I was trying to convey that my scripts just got shorter and shorter.”

Their run on Astonishing X-Men began in 2004 — and came with a dramatic change: In their first issue, they brought back the team’s colorful uniforms, after the characters had worn black leather for many years. Whedon addressed the new looks with his trademark wit, having Cyclops tell his fellow mutants, “Sorry, Logan. Superheroes wear costumes,” and, “All the black leather is making people nervous.”

Whedon and Cassaday also brought Colossus, a character who was believed to be dead, back to the team. The reveal is a testament to how well the creative team meshed.

“The best page I ever wrote in comics has no words,” Whedon said. The page, which also has no sound effects, depicts Kitty Pryde, Colossus’ lover, gazing at him with a stunned expression as she places a hand over her heart.

“He didn’t swagger; he didn’t yell,” Whedon said of Cassaday, but “he was very exacting” about his art — an approach that included giving notes on the colors and lettering of his pages.

Laura J. Martin, the colorist on Astonishing X-Men, said that one of her favorite collaborations with Cassaday was the cover of No. 6 in the series, on which he depicted Kitty and Colossus caressing. The cover required extensive color work to convey texture and the silver sheen of Colossus’ metallic body. Cassaday gave Martin that cover as a wedding present.

Cassaday “was definitely a perfectionist,” said Chris Eliopoulos, the letterer on Astonishing X-Men. “Our first issue of Astonishing was like a class. I had to learn what he wanted.” One lesson: Cassaday liked symmetry. Another: He did not like colored word balloons.

Eliopoulos applied this knowledge when he worked with Cassaday on a new Star Wars comic book series, written by Jason Aaron for Marvel in 2015. An editor suggested black word balloons for Darth Vader. Eliopoulos told the editor that Cassaday would not like that. Undeterred, the editor went and asked Cassaday, and he responded, “No, we’re not doing that.”

The first issue of that series sold more than 1 million copies.

Johnny Mac Cassaday was born Dec. 14, 1971, in Fort Worth, Texas, to Johnny Mac and Latrell Cassaday. His father was a deputy fire chief, and his mother was a hairdresser.

Cassaday studied film at the University of North Texas but did not graduate. He then worked as a news director for a television station in Denison, Texas, from 1990 to 1995.

“His love of news stayed with him. He’d often have it on when he was drawing,” Martinez, his partner, wrote in an email. “I’d chuckle when he’d get distracted and start backseat directing the broadcast.”

In addition to Martinez, he is survived by his mother and a sister, Robin Cassaday. His father died of cancer in 1990.

Cassaday broke into the comic book industry in 1994 with a one-page illustration and a short story for Boneyard Press. Other assignments followed, and a portfolio review in 1996 with Waid, who was a freelancer then, helped propel him to the next level.

Waid recommended Cassaday to writer Jeff Mariotte, with whom he would create the series Desperadoes, a weird take on the Wild West, which was published the next year.

“I refuse to take any real credit for ‘discovering’ John Cassaday,” Waid wrote on Facebook. “I can’t take credit for having functioning eyeballs.”

In 2019, Cassaday became the chief creative officer of the comic publisher Humanoids, where he began work on Madshadows, a passion project about the pulp magazine stories and characters of the early 20th century. Cassaday was writing and drawing the project and had completed dozens of pages at his death.

“He considered it his magnum opus,” Martinez said. “I hope the world gets to see it someday.”

This article originally appeared in The New York Times.