Word Bearers during the Heresy / siege

[Uprising]

I was wondering, when / event did the Word Bearers become the chaos space marine we know today during the Horus Heresy?  Curious as most of the traitor legion seem to be there current chaotic self be the time of the siege.  

[lansalt]

Going by Know No Fear and other stories,  it was during the battle of Calth and the Shadow Crusade. At that point they no longer had to keep pretending.

[Uprising]

19 hours ago, lansalt said:

Going by Know No Fear and other stories,  it was during the battle of Calth and the Shadow Crusade. At that point they no longer had to keep pretending.

You make a good point, forgot about the shadow crusade.  Thank you.  

[jaska]

Yeah it was definitely a sliding process rather than "hey we're CSM now".

 

Something like  Monarchia/Emperor's rebuke -> pilgrimage to the Eye of Terror -> shadow crusade -> dropsite massacre -> daemonic ascension -> siege

 

So they had certainly fully embraced chaos (ideologically) before the Heresy, but the physical/operational transformaton was solidified during it. By the SoT, they had fully integrated chaos rituals/warpcraft/etc.  I'd say the pilgrimage they made was probably the real point of no return as that's when Lorgar really embraced chaos and communed with it, and when they revealed the Imperial Truth was... not True.