Dennis Detwiller started volunteering at Pagan Publishing after seeing an issue of The Unspeakable Oath magazine in 1991 and talking to John Scott Tynes.

[2]: 245  Detwiller worked at Pagan as art director where he co-created the Origins Award-winning game Delta Green in 1997 with Tynes and Adam Scott Glancy;[3][4] Detwiller wrote a series of three chapbooks (1998–2000), and with Tynes and Glancy he expanded the setting in 1999 with Delta Green: Countdown.

[4] Detwiller and Ivey wrote Delta Green: Targets of Opportunity (2010) and also brought back The Unspeakable Oath in 2010.

[2]: 250  Following a successful kickstarter campaign, Arc Dream publishing announced a new Delta Green game to be released in 2016.

[7] In 2002, he left Seattle for Vancouver to work with Radical Entertainment[1] where he helped develop The Incredible Hulk: Ultimate Destruction, Scarface: The World is Yours and Prototype.