Large-scale incumbent organizations face pressure to modularize their IT architecture to maintain competitiveness. This transformation involves navigating technical, organizational, and business dimensions, favoring a socio-technical perspective. Traditionally, IS literature views IT architecture as a support mechanism for business operations. However, emerging digital technologies exert influence that reshapes physical realities. We propose an IT architecture viewpoint that prioritizes technology as a catalyst for organizational change. Our research question is how can architectural transformation be managed in large-scale incumbent organizations? The empirical evidence is a study of a large-scale financial institution in Norway, where we analyse an architectural transformation process. We offer two contributions; first, we identify three core processes and demonstrate their connection. Second, we theorize architectural transformation by comparing it with three important IS streams. Through this, we distinguish between architecture-as-servant and architecture-as-transformer and propose that architectural transformation more explicitly focuses on the role of IT architecture in transformation processes.