The Ferrum was a Strike Cruiser of the Iron Hands during the Great Crusade and Horus Heresy. Named after the Iron Hands Primarch Ferrus Manus, the Ferrum was commanded by Captain Balhaan during the later days of the Crusade, where it participated in the war against the Diasporex. During the campaign, Balhaan failed in his duty in destroying a small enemy fleet. Though Ferrus Manus was tempted to take Balhaan's head off for his failure, his Equerry advised him to instead place an Iron Father in joint command of the Ferrum as punishment.
Later, the Ferrum became the temporary flagship of Ferrus Manus during the campaign on Isstvan V after the Fist of Iron was crippled in a confrontation with Fulgrim and the Emperor's Children. As the loyalists were massacred in the subsequent Drop Site Massacre, most of the Iron Hands fleet was destroyed by the traitors in orbit but the ultimate fate of the Ferrum remains unknown.