Perturabo: The Hammer of Olympia: Primarchs: The Horus Heresy, Book 4 (Unabridged‪)‬

Born to a life of political conflict, Perturabo was always considered a child prodigy among the people of Olympia - indeed, his philosophical and scientific works were beyond compare. But then, after his rediscovery by the Emperor and decades of thankless military campaigning on the Great Crusade, the primarch begins to resent his Legion's place in the Imperium.

When word reaches him of turmoil on his adoptive home world, he orders the Iron Warriors to abandon their campaign against the alien hrud and crush this emerging rebellion by any means necessary....