Lucius is a Commander on the Emperor's Children Chaos Space Marine Legion, pre-Heresy, Lucius was looking into perfection like his Primarch Fulgrim, Slaanesh promised perfection in all things if they worshipped him(with Horus already corrupted, turning them traitor wasn't a hard task to accomplish) Lucius became one of the most skillful swordsmen in the galaxy, none could best him in Sword play. Fulgrim set up gladatorial arena's for when combat was lacking for his warriors to test themselves n combat, However this all changed with Lucius, he won combat after combat, but this all changed with Cyrius, a Chaos Commander whom actually bested Lucius in combat, however, Slaanesh was loathe to see his most prized fighter fall, over a course of weeks, Cyrius's body began to change, hair began to fall out in clumps, black stripes began emarging from his skin, all that was left of Cyrius was a writhing, screaming face on Lucius's armor and for that moment on, anyone who took even a brief amount of pride conquering Lucius was doomed to turn into him.
Lucius the Eternal