Warhammer 40k - Space Marines Codex Supplement - Sentinels of Terra

The Imperial Fists have defended the Imperium since the days of the Great Crusade. They stood with the Emperor at the Siege of Terra, and have continued his life's work in the centuries since. They are indefatigable defenders of Mankind, and the foremost guardians of Terra itself.

(Don't ask me why this thing thinks it's a Necron Codex, I don't know anymore.)