Redemption Crusades

The Redemption Crusades were a series of Imperial Crusades fought by the Imperium of Man during the era known as The Waning in the 39th Millennium. They succeeded in greatly expanding the borders of Imperial space.

History
In 131.M39, the so-called "Redemption Crusades" began. In each of the segmentums of the Imperium a great hero emerged. Like unto the Primarchs of old were these warriors, and the combined efforts of their Imperial Crusades pushed back the borders of the Imperium further than they had been for nearly 500 standard years.

And then, 50 Terran years later, the five heroes vanished without a trace, spurring Ecclesiarch Inovian III to declare them Imperial Saints returned to the Emperor's side.