He was the youngest artist in the history of pioneering role-playing game company TSR when he began his work at the age of 18.

[1] In the late 1970s, while Dee was still a teenager, he and Jack Herman created Villains and Vigilantes, the first complete superhero role-playing game.

[3]: 104 Dee was the youngest artist in TSR history when he began working for them at the age of 18.

[4] In 1997, with his partner 'Manda, Dee founded UNIgames, a publisher of role-playing, board, and computer games.

[citation needed] Dee designed a new superhero role-playing game originally titled Advanced Villains and Vigilantes, which was ultimately published as Living Legends in 2005.