The Legiones Astartes, also known as the Legions Imperialis, are the original twenty Space Marine Legions created by the Emperor of Mankind during the Great Crusade era of Warhammer 40,000. Each Legion was comprised of genetically-enhanced superhuman warriors known as Space Marines, led by their Primarchs—genetically engineered demigod-like beings. These Legions were instrumental in expanding the Imperium across the galaxy, using advanced technology, powerful weaponry, and unwavering loyalty to the Emperor. After the Horus Heresy, the Legions were divided into smaller chapters to prevent another catastrophic civil war within the Imperium.