Gaul for Old World is a free mod designed for Windows that introduces a new playable empire, the Gauls, to the game. The mod replaces the existing tribe with a Celtic-themed tribe led by the young founder Brennos, featuring distinct family units such as Senone, Salyes, Arverne, and Parisii, each with unique roles. The mod also incorporates paganism elements, showcasing shrines dedicated to Teutates, Belenos, Epona, and Icovellauna, with custom 3D models for some of these shrines. Unique units like the Essed and Trimarcisia add depth to gameplay, emphasizing tactical advantages without the risk of routing.

Currently in alpha state, this mod aims to enhance the game with future updates that include a comprehensive overhaul focusing on forests, additional Gaul-specific events, and improved 3D models for towns and units. Players can look forward to a Gaul scenario campaign that includes multiple chapters, such as Brennos's military endeavors against Rome and scenarios highlighting trade and resistance against Caesar's legions. Feedback and bug reports are encouraged to aid in the mod's development.