Chaos Space Marines must kill everything and let the galaxies burn. They are fallen Adeptus Astartes of who fell to Chaos 10,000 years ago, at the start of the Horus Heresy in the 30th Millenia mainly led by the then Warmaster Horus Lupercal, Primarch of the Luna Wolves (now Black Legion), who decided that he was stronger and more just than the Emperor, and they had a great war, the said Horus Heresy, that destroyed many planets. Horus nearly won, even reaching Holy Terra in his conquests, but the Emperor and his forces was stronger. In the end, Horus was killed by the Emperor's sacrifice and the Astartes that had followed him/ generally fell to Chaos but did not join Horus went to the Eye of Terror, where they still live. Chaos Marines look extremely different to regular Space Marines, and often have spiky protrusions, skulls and mutations. They also have special units that are dedicated to their gods and are useful in different roles. At the time of the Horus Heresy 9 of the 18 total Astartes legions fell to Chaos these include: Luna Wolves (now Black Legion, Thousand Sons, Death Guard, World Eaters, Word Bearers, Night Lords, Alpha Legion, Iron Warriors and 