DOOM: The Dark Ages has a total of 22 chapters. These chapters vary in length and design, ranging from linear levels to more open, expansive battlefields with secrets and challenges to discover

. Here is the full list of chapters in chronological order:

• Village of Khalim
• Hebeth
• Barrier Core
• Sentinel Barracks
• The Holy City of Aratum
• Siege – Part 1
• Siege – Part 2
• Abyssal Forest
• Ancestral Forge
• The Forsaken Plains
• Hellbreaker
• Sentinel Command Station
• From Beyond
• Spire of Nerathul
• City of Ry’uul
• The Kar’Thul Marshes
• Temple of Lomarith
• Belly of the Beast
• Harbor of Souls
• Resurrection
• Final Battle
• Reckoning

Most chapters take around 30 minutes to complete, with the entire game requiring roughly 15 to 25 hours depending on difficulty and exploration level

. The game also features numerous secrets and challenges across these chapters, contributing to its replayability and depth

. In summary, DOOM: The Dark Ages consists of 22 chapters that together form a substantial and varied campaign experience.