Zardu Layak (real name unknown), also known as the Crimson Apostle, was a member of the Word Bearers during the Horus Heresy. Once an officer in the Ashen Circle born on Terra, he oversaw the burning of churches and temples in the Emperor's service during the Unification Wars.
Following the legion's humiliation at the hands of the Emperor, Layak eagerly embraced the teaching of his Primarch Lorgar as well as those of Erebus and Kor Phaeron. However even these did not fill the void in him, and he soon began having visions of his Primarch speaking directly to him, telling him to not burn books but rather learn from and covet them and eventually discover the truth the Emperor had kept from his sons. Ashamed, he kept these visions from his comrades.
Eventually he took a new name from the Book of Lorgar, was reborn as one of the Gal Vorbak, and became First Chaplain of the Chapter of the Ochre Gate, which after he corrupted its members became known as the Unspeaking. He went on to participate in the Battle of Calth.