Originally Posted by
entendre_entendre
yeah, one of the baby primarchs was killed, or possibly injured/mutated by horus when he went back in time (the XI legion? i don't remember)
i always thought the forgotten legions were removed b/c they didn't choose a side in the heresy, i don't really have evidence for this and the passage from the HH series about "two more legions" may or may not defeat this.
the "two more legions" could be the imperial fists due to their favour w/ the emperor & the ultrasmurfs b/c gulliman was a chief rival of horus so would never join him. w/e it's just fun speculation :)