XIII is a unique first-person shooter that immerses players in a visually striking cel-shaded world inspired by the acclaimed Belgian comic series. The game revolves around a gripping conspiracy, where players must piece together clues to uncover the truth. The environment is filled with comic book aesthetics, enhancing the immersive experience as players navigate through various levels globally. The narrative is complemented by innovative visual storytelling, where actions like headshots are represented through a series of still images, adding to the comic book feel.

Gameplay includes a mix of stealth and action elements, with over fifteen distinct weapons available, such as shotguns and crossbows. Players can interact with various environmental objects and face numerous enemies throughout their journey. Additionally, the game allows players to develop skills like silent walking, lockpicking, and dual weapon handling, providing a diverse range of gameplay mechanics that cater to different playstyles.