Critchlow's comic book career began in the early 1980s, when he contributed to fanzines and informal publications. His professional career began in 1983 when his work was published in Issue 45 of Games Workshop's "White Dwarf" magazine, where Critchlow first portrayed his fantasy barbarian character, "Thrud the Barbarian", in a regular, page-long, black and white, ink-drawn strip of the same name. Thrud was published for over fours years until issue 106; the strip was voted 'most popular feature' for three years running in readers' polls. "Thrud the Barbarian" often reflected current Games Workshop product lines and borrowed themes from games like , Blood Bowl and Warhammer 40,000 and Thrud's native fantasy theme. To celebrate the character's status as a popular feature of the publication, Citadel produced a number of metal miniatures of Thrud. Shannon Appelcline referred to Bil's "Gobbledigook" and "Thrud the Barbarian" as the two comics "for which "White Dwarf" is probably best known". Critchlow also provided numerous black and white interior illustrations for Games Workshop's Dark Future game, and was featured in an "Illuminations" exposè in White Dwarf issue 103.