The third mission of Doom: The Dark Ages, Barrier Core, is a titan-only section with no secrets to find. That's only a short-lived reprieve as the fourth mission kicks things up a gear. Not only are there nine Sentinel Barracks secrets and three collectibles, but rubies are also thrown into the mix, letting you upgrade gear to the next tier.
Fear not, though, I've done the heavy lifting to find all the Doom: The Dark Ages secrets in the Sentinel Barracks mission. Below you'll find all the secrets and collectibles laid out in chronological order, so you don't miss anything the first time through.
