Denna passage är inte historiskt faktum. Istället är det något som sägs att Lorgar får honom längre ner på vägen till kaos.
Jag vet inte om något som tyder på att Khorne, Slannesh, Tezench eller Nurgle någonsin var dödliga.
Efter lite forskning hittade jag följande:
Författaren, ADB, själv säger (på länken ) :
It's a parable, about 4 travellers leaving Colchis and finding some vague truth / travelling to that region of space before it was the Eye / a reference to how Colchisians have always been pilgrims / a reference to how Chaos is eternal / a suggestion that a Chaos presence was always in that region of space to some degree and that humanity has forever been drawn to it / a way of suggesting to the Colchisian characters in the novel that their homeworld has always been chosen and inspired by Chaos.
It's not saying anything specific, and for the record, nor is it a retcon. It's a throwaway line about a legend. It's impossible that it could ever make sense. So obviously, it doesn't. Just a Colchisian version of the Odyssey, or the Bible, or the Mahabarat.