The Codex: Deathwatch contains the following inside of its pages:
- The history of the Deathwatch
- A Deathwatch bestiary
- Images of painted Citadel miniatures
- Rules for Space Marines units available to the Deathwatch
- Rules for fielding mixed units and Kill Teams
- Stratagems, Warlord Traits, the bespoke Xenopurge psychic discipline, Relics of the Deathwatch, and optional secondary objectives that define the ways that the Deathwatch wage war
- Crusade rules providing new Agendas, Requisitions, Battle Traits, Honorifics, and Crusade Relics