For fans of a certain kind of animation, Monty Oum was the Wizard — and the King, the Knight and the Pawn, all rolled into one. Millions of people watched his web series “Red vs. Blue” and “RWBY.” At conventions, thousands of fans, sometimes dolled up in the outfits of fantasy characters he created, waited for hours just to meet him.

Even in a scene known for its colorful personalities, Mr. Oum stood out. Clad in often over-the-top anime-style costumes — platinum wigs, rubber vests — with an unabashed energy and a robust work ethic, he served as an inspiration to audiences weaned on a D.I.Y. techno-culture.

So when his death was announced on Monday, there was an outsize outpouring of grief online — heartfelt tributes and teary condolences on Tumblr, Twitter, Reddit, Facebook, YouTube, even Google Docs.

“He changed my life and my outlook on work and creativity, on being a good person and a good friend,” said one, from the cartoonist Arin Hanson.