Work
Chaosium
He became a full-time staff member at Chaosium. His interest for role-playing games and H. P. Lovecraft were fused when he became principal author of Chaosium's game Call of Cthulhu, published 1981, and many scenarios and background pieces thereafter.
He authored several critically acclaimed RuneQuest supplements for Avalon Hill and Games Workshop. Petersen served as co-designer for West End Games's Ghostbusters role-playing game.
MicroProse
He worked some time for MicroProse, where he is credited for work on Sid Meier's Pirates! and Sword of the Samurai. Between 1989 and 1992 he worked on the video games Darklands, Hyperspeed, and Lightspeed. He made some contributions to Civilization.[citation needed] Petersen was laid off in 1992 and was jobless for 5 months. He considered that period as one of the worst times of his life.
Ensemble Studios
He left id Software for Ensemble Studios in June 1997. There, he worked as a game designer on several of their Age of Empires titles, including Rise of Rome, Age of Kings, and The Conquerors. During this time, he was a frequent poster on the HeavenGames forums under the username ES_Sandyman. He ran a popular series of threads, "Ask Sandyman", where forum members could ask him about anything they wanted.
Other works
Petersen was the executive producer for the 2011 film The Whisperer in Darkness which was nominated for awards at the Chicago International Film Festival and Warsaw International Film Festival. It was produced by H.P. Lovecraft Historical Society Motion Pictures in the style of a 1930s black and white horror film.[citation needed]
In April 2011 he served as the publisher of horror magazine Arcane: Penny Dreadfuls for the 21st Century.
Petersen took a professorship at The Guildhall at SMU in 2009 following the closure of Ensemble Studios, where he taught several courses on game design.
Petersen worked at Barking Lizards Technologies as their creative director, after leaving The Guildhall, and worked on their iOS release Osiris Legends.[citation needed]
In mid-2013 Petersen led a successful Kickstarter campaign by his company, Green Eye Games, to produce the boardgame Cthulhu Wars. Over US$1,400,000 was raised achieving over 3,500% of the initial target. This success allowed the creation of more figures (60), map expansions and additional scenario options. Green Eye Games also produced the unsuccessful kickstarter Cthulhu World Combat (iOS, Android, Windows, PSN, Xbox Live).
In June 2015, it was announced that Petersen and Greg Stafford returned to Chaosium Inc. Petersen retired from the board in 2019, but continues to do occasional freelance work for the company.
