The planet of Caliban exists much as it has for thousands of years the knightly orders protect the common people, fighting back the beasts that lurk in the depths of the seemingly endless forests. Young Zahariel and Nemiel aspire to join the greatest of the orders, led by the example of mighty Lion El’Jonson and his vision of a peaceful and unified world. But the coming of the Imperium brings new concerns and a new destiny for the Lion as part of the Great Crusade, and the sons of Caliban must decide if they will follow him to glory among the stars.

Read it because
It's a fascinating insight into a world that's home to a primarch before it comes into contact with the Imperium, and the changes that are made when the Space Marines arrive. It also sets up the darkness that we know lies in the heart of the Dark Angels as the Heresy progresses...

The eBook edition includes integrated illustrations of characters and events from the story, and an afterword that places the story in context within the series.