Carandiru

Carandiru, penal world of the Imperium, was first brought to compliance by Rogal Dorn during the Great Crusade. During the Horus Heresy it fell to the Sons of Horus, who delivered its prisoners, many of them loyal Imperial citizens, into the hands of Fabius Bile for experimentation of the most grotesque kind. An uprising raised among the inmates by Commander Soukhounou drew the Raven Guard under Corax to the world’s liberation; in the fighting, Corax himself was nearly overwhelmed by Bile’s Enhanced Warriors before the planet was retaken.