Chaos Uprising

The Chaos Uprising is where Roboute Guilliman rose up against the Emperor of Mankind and defeated him.

Forces
Pre-Heresy

2 they kept their numbers low to hide from the Imperium

3Their numbers never above 100,000 in the original universe so i'm going for a lower number

4Legion is being currently being a council who all control portions of the Sons of Horus.

Post-Heresy

Aftermath

 * Terra is destroyed
 * Imperium is destroyed
 * The Lost Legions come out of hiding
 * The Empire of Light, Chaos Imperium, and Dragocis Novus are founded
 * Many Space Marine Legions are shattered and are brought to near extinction