The Ultramarines are considered one of the strongest and most honoured of all the Space Marine Chapters in the Imperium of Man, and were responsible for almost single-handedly holding the Imperium together after the Horus Heresy. Highly disciplined and courageous warriors, the Ultramarines have remained true to the teachings of their Primarch Roboute Guilliman for 10,000 standard years. The Ultramarines were originally the XIIIth Space Marine Legion before the reforms that initiated the Second Founding and reshaped the Imperium after the Heresy on the orders of Guilliman himself as the lord commander of the Imperium and Imperial Regent.