Known as the Occuli Imperator or "The Emperor's eyes", Aquillon oversaw the progress of Imperial forces in the the Crusade and reported it back to the Emperor. Aquillon was captain of the Custodes unit assigned to watch over the Word Bearers after their scolding by the Emperor at Monarchia and took part in the Battle of 47-16 at the side of those he was reporting on. Aquillon failed to disover the fall of the Word Bearers to Chaos and was deceived for many years. When the time was right Lorgar had all the Custodes accompanying his forces massacred so they may not inform the Emperor of the Drop Site Massacre. Aquillon was killed when his head was bitten off by the Possessed Chaos Space Marine Argel Tal, who was enraged over the death of Cyrene Valantion.