The Primaris Space Marines are a new breed of transhuman warriors. They have been genetically altered by Archmagos Dominus Belisarius Cawl to be bigger, faster and stronger than their Space Marine brethren.
Primaris Space Marines are bigger – standing from 8 to nearly 10 feet tall (approximately 2.5 to 3 metres) in their armour in some cases – more resilient, physically more powerful and possess faster reaction times than their original Astartes counterparts, now often referred to as the “Firstborn.”
Raised in what became known as the Ultima Founding, the Primaris Marines were deployed across the galaxy during the Indomitus Crusade by Guilliman and Cawl after the opening of the Great Rift. They were used as reinforcements for existing Chapters of Astartes or to found all-new Chapters comprised solely of Primaris Marines.