Ultramarine

"Ultramarines are now part of the Future Alliance, thanks to Miles Callisto. Now the Imperium of Man's part of this cool alliance. Wasn't it beautiful about this?"

--Su Ji-Hoon, Justice With the Common Good

Ultramarines are considered one of the strongest and most honored 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 XIII Space Marine Legion before the reforms that initiated the Second Founding and reshaped the Imperium after the Heresy on the orders of Guilliman himself.

In When the Cold Breeze Blows Away, they serve for the Future Alliance.