Backed by a large AAA budget, the Thief team expanded rapidly. While the project attracted a few designers, programmers and artists from across the globe, many came from other Montreal studios. A number of senior team members previously worked together at Ubisoft Montreal, and were quick to recruit local colleagues. According to one source, collegial favoritism began to divide the office.

The lead and senior design roles were fluid, with some team members departing after less than two years. According to one source, each new lead and senior designer would come with a new vision for the game. Old ideas - including stages and mechanics - would be rebuilt or scrapped. In March of this year, the same month as the game's publicity push on the cover of Game Informer magazine, Lead Game Designer Dominic Fleury left the studio.

Sources emphasized the high level of talent and enthusiasm of team members, many of whom came to work on Thief because of their love of the franchise. Those same sources cited team politics and conflicting visions as cause for many departures and setbacks.

Due to a need to hit promotional deadlines, the latter part of 2012 and early 2013 was focused on creating press demos, the first of which was shown for the Game Informer cover and also at last month's Game Developers Conference. According to a source, the demo took nearly 10 months of development time, roughly six of which required the participation of nearly every content creator on the team. The level, which takes place in part inside a brothel, apparently featured "Cinemax-level" sex sequences at one point that some animators were uncomfortable creating.