The Rubicon Can Wait: Let's hear your lore for fielding Firstborn in M42.
Brothers of the Firstborn,
As the Era Indomitus grinds on and the Primaris standard takes over both the lore and the tabletop, I find myself wondering how the rest of you justify keeping your classic Firstborn on the front lines.
Are your veterans simply too stubborn to risk the Rubicon? Does your Inner Circle harbor a deep-seated paranoia regarding Belisarius Cawl and his "innovations"? Or is your chapter fighting a forgotten war in the dark corners of the Imperium, cut off from Guilliman's logistical supply lines?
My own Dornian successors, the Knights Praetor, remain Firstborn out of rigid traditionalism. To them, the Rubicon Primaris is an unacceptable cultural and mortal risk. They firmly believe that Rogal Dorn would view Cawl's tampering with the Emperor's original genetic design as heresy, much like his initial, bitter defiance in the face of the organizational changes wrought upon the Emperor's legions by Guilliman's Codex Astartes. Because of this, the Knights Praetor maintain an insular, radical purity of purpose—relying exclusively on the ancient wargear, unaltered genetics, and stoic attitudes that have sustained them for centuries.
Let's hear your chapter's lore. What narrative hooks keep your Firstborn marching to war in M42?