Space Marines Primaris
The Primaris Space Marines are a new breed of transhuman warriors developed across the span of ten thousand standard years by Archmagos Dominus Belisarius Cawl on Mars on the order of Primarch Roboute Guilliman in the days immediately after the Second Founding in the early 31st Millennium. Cawl used the genetic template of the original Space Marines created by the Emperor for His Great Crusade as the starting point for the development of these new Astartes.
Primaris Space Marines are bigger, more resilient, physically more powerful and possess faster reaction times than their original Astartes counterparts. Primaris Astartes are also implanted with 22 rather than 19 gene-seed organs, and their gene-seed is more resistant to mutation than that of their predecessors. They were deployed across the galaxy by Guilliman and Cawl during the Indomitus Crusade after the opening of the Great Rift where they were used as reinforcements for existing Chapters of Astartes or were used to found all-new Chapters comprised solely of Primaris Marines.