It's the 30th Millennium, Terra (formally called Earth) is in the Age of Strife, after 5 millennia after the Cybernetic revolt ended and Warp storms began, a man who's been around Terra since the late dawn of humanity, the Emperor of Man reveals himself as a Warlord who's goal is to retake all of Terra and unify it under a single banner. He creates super soldiers called Thunder Warriors (precursors to the Space Marines) who came from the techno-barbarians of Terra and the Emperor took over Terra and then Luna (aka, the moon). After that, he began to work on the Primarch Project, 20 artificially created generals that we're kinda like his sons. However, the Chaos Gods separated all of the gestating sons via the Warp to random planets. However, the Emperor used the leftover genetic material to improve the Thunder Warriors, creating Space Marines, and after the Warp storms settled after the birth of the Chaos God, Slaanesh. He embarked on a Great Crusade to unite all of humanity and to find the rest of his sons. He found the 16th Primarch, Horus first and found them all as the years past. As the dawn of the 31st Millennium was approaching, Lorgar, Primarch of the Word Bearers, went on a pilgrimage in the Eye of Terror, a permanent Warp storm created by the birth of Slaanesh, and he and his legion were corrupted by Chaos and began to plot the Imperium's demise. First, they poisoned Horus (now Warmaster) with a Nurgle corrupted blade on Davin that the legion apothecaries didn't know how to stop it, so they gave Horus to the local humans of Davin be cured. However, the humans were Chaos worshippers and both cured him, and corrupted him into joining Chaos. Magnus tried to warn the Emperor (who was trying to build a Terran webway system so that humanity didn't have to rely on the Warp) but he couldn't, so he made a deal with Tzeentch (who's a Chaos god) and broke the webway, causing thousands of daemons to flood it and he tried to warn the Emperor, but he ignored him, causing Magnus's fall to Chaos. The first major battle of the Horus Heresy was on the planet, Istvaan III, when the Imperium (unaware of Horus's corruption) charged Horus to stop the revolt caused by the Slaanshie corrupted populous, he ended up corrupting the Death Guard, Emperor's Children, Sons of Horus (his own legion), and the World Eaters. After a long battle, Horus virus bombed the planet, causing everything (including Space Marines) to decay into a plie of goo. After 9 years of civil war,
