Brian Michael Bendis, a 20-year Marvel veteran, will join DC Comics, the publisher announced today. Not only will Bendis be writing DC Comics characters for nearly the first time, he’ll be writing them exclusively, breaking ties with Marvel Comics.

So Bendis’ move is surprising: Usually, when DC or Marvel announce exclusivity agreements, they’re with writers and artists who have already been working with them off and on for a while, with a few successful home-publisher titles under their belts. Occasionally, DC or Marvel will exclusively sign new, up-and-coming talent. The announcement of a major company switch for a name as big as Bendis, who has virtually never written for DC before, is unusual.

But it’s also unusual because, love his work or hate it, Bendis has made major contributions to the foundation of the modern Marvel Universe. Comparisons are already being made to Jack Kirby’s 1970 defection from Marvel to DC Comics. Bendis not just a writer primarily known for Marvel work — you could argue that modern Marvel is a company known for Bendis’ work.

Bendis’ very first comic for Marvel, 2000’s Ultimate Spider-Man, was an instant hit. Set in an alternate universe from the main Marvel timeline, the book restarted Peter Parker’s story from the beginning, modernizing Spider-Man’s origin for new readers and jettisoning 40 years of backstory. Marvel’s Ultimate Universe was a huge financial success for the company, thanks in part to the popularity of Ultimate Spider-Man, which often outsold the main-universe’s The Amazing Spider-Man month-to-month.

For more on exactly how huge the Ultimate Universe was for Marvel, and Bendis’ role in it, see Polygon’s episode of Issue at Hand:

Bendis and artist Mark Bagley’s 111-issue streak of partnership on Ultimate Spider-Man is the longest consecutive artist/writer collaboration on a single book in Marvel history — even longer than Stan Lee and Jack Kirby’s seminal run on The Fantastic Four.

When Bendis returned to the series in 2011, he anchored another milestone (no pun intended) in Marvel history with the introduction of Miles Morales, making headlines for killing Peter Parker and introducing a young man of African-American and Puerto Rican descent as the Ultimate Universe’s new Spider-Man. Miles’ popularity made him one of the few characters integrated into the main Marvel setting when the Ultimate Universe line was shuttered in the 2015 Secret Wars event.

But Bendis’ Marvel work isn’t just about Spider-Man. In the intervening decade, the writer’s work on Daredevil was already significant enough to be referenced in 2003’s Daredevil movie. Only a year after starting Ultimate Spider-Man, he helped launch Marvel’s “Marvel Max” imprint, for stories containing adult content, with a super-powered private eye series called Alias.

Bendis is no stranger to noir and crime stories, with his superhero-tinted police procedural Powers, which was adapted into a show that ran for two seasons on Playstation Network. And the star of Alias, Jessica Jones, is now better known than its title, following her eponymous Peabody award-winning Netflix series that ties into the Marvel Cinematic Universe.

In Alias, Bendis breathed new life into the then dated and hokey character of Luke Cage, and brought the character to new prominence when Bendis was given the opportunity to reform the Avengers, Marvel’s flagship superhero team, in The New Avengers. In his time in the Avengers office, he oversaw a trio of big Marvel crossover events still remembered today — Avengers Disassembled, in which paved the way for a relaunch of Avengers-related titles; House of M, in which the Scarlet Witch had a mental break and altered reality into one in which Mutants ruled human society; and Secret Invasion, in which it was revealed that the shapeshifting Skrulls had secretly replaced and been posing as several major superheroes as a prelude to a full scale invasion of Earth.

Bendis also wrote the Age of Ultron crossover, which lent its name to 2015’s Avengers: Age of Ultron film; and, if you’ve been following along with the X-Men books in the past few years, he’s responsible for the plot events that brought teenage versions of the five original X-Men into the present day of the Marvel Universe.

Bendis is divisive as a comics writer — while most fans would agree that his work on Spider-Man and Jessica Jones is undeniably great, the plots of his crossover events remain controversial, with complaints about character writing and canonical inconsistencies.

He’s also famous — or infamous, depending on whether you like it — for his characteristically conversational dialogue, which often spins out into stacks of alternating balloons as characters share one or two words with each other over the course of a panel packed with bubbles.

And while his work on creating and popularizing characters of color like Miles Morales, Luke Cage and Riri Williams (Ironheart) for the Marvel Universe is lauded, it’s also become something of a tired trend to many fans. Why is a white writer like Brian Michael Bendis (albeit a writer with children of color) so often given the opportunity to craft these characters, the argument goes, when Marvel could be diversifying its universe in and out of fiction, by hiring more creators of color?

Reaction to Bendis’ move to DC is being greeted with both excitement and concern by DC and Marvel fans alike. It’s anyone’s guess at what facet of the DC Comics universe Bendis will be tackling first — this writer could only find one DC Comics story he’s ever written, in a more than 20-year career. “Citizen Wayne” appeared in issue #21 of the anthology series Batman Chronicles; a recasting of Citizen Kane with Batman characters told in starkly lit black and white, in which a reporter named Kent searches for the meaning behind the last words of a the mysterious and powerful billionaire, Bruce Wayne.

It may have been a little-known story from a little-known comic, but it was a title I recognized immediately. I read it once in high school and have never quite forgotten it. Good or bad, fan-loved or -hated, this longtime DC Comics reader is very surprised to see Bendis at DC, and very interested to see where he goes from here.