Short answers, pulled from the story.
Dave Arneson was an American game designer born on the 1st of October 1947, best known for co-creating Dungeons and Dragons with Gary Gygax in the early 1970s. He invented foundational role-playing game concepts including hit points, armor class, the dungeon crawl, and the neutral referee who voices all non-player characters.
Arneson met Gygax at the second Gen Con gaming convention in August 1969, when Arneson was a history student at the University of Minnesota. The two discovered a shared interest in sailing ship games and went on to co-author naval battle rules before collaborating on Dungeons and Dragons.
Blackmoor was a medieval fantasy game setting Arneson developed in 1971, played with the Twin Cities Military Miniatures Group. It introduced the dungeon crawl, hit points, armor class, and character development, and also incorporated time travel and science fiction elements including steam power, gunpowder, and submarines.
Arneson filed the first of five lawsuits against TSR and Gygax in 1979 after TSR refused to pay him royalties on Advanced Dungeons and Dragons, claiming it was a significantly different product from the original D&D. The suits were settled out of court in March 1981, giving Arneson co-creator credit and a 2.5% royalty on all AD&D products.
Arneson taught computer game design at Full Sail University starting in the 1990s and continued until 2008. His course, called "Rules of the Game," trained students to create and accurately document balanced game rule sets.
Arneson died on the 7th of April 2009, after battling cancer for two years. Wizards of the Coast replaced the front page of their Dungeons and Dragons website with a tribute, Activision Blizzard posted a tribute online, and World of Warcraft patch 3.1 released on the 14th of April 2009 was dedicated to him. Full Sail University named its student game development studio Dave Arneson's Blackmoor Studios on the 30th of October 2010.