Gygax and Jeff Perren wrote Chainmail, the game from which D&D was developed, in the late 1960s. Gygax and Kaye founded publishing company Tactical Studies Rules (TSR) and published the first version of D&D in 1974. Gygax wrote a new version of D&D, Advanced Dungeons & Dragons, which was published in 1977-9. As of 2003, Gygax continues to take an active role in D&D, and writes a section in Dragon Magazine.
Another of his creations was DragonChess, a three-dimensional fantasy chess variant, published in Dragon Magazine #100 (August 1985). It is played on three 8x12 boards stacked on top of each other - the top board represents the sky, the middle is the ground, and the bottom is the underworld. The pieces are characters and monsters inspired by the Dungeons and Dragons setting: King, Mage, Paladin, Cleric, Dragon, Griffin, Oliphant, Hero, Thief, Elemental, Basilisk, Unicorn, Dwarf, Sylph and Warrior.
After leaving TSR Gygax created Dangerous Journeys, an advanced RPG spanning multiple genres. He began work in 1995 on a major new RPG, originally intended for a computer game, but in 1999 released as Lejendary Adventure which some consider to be his best work to date. A key part of its design was to keep the gaming rules as simple as possible, as Gygax felt that RPGs were becoming too complex and discouraged new users.