In the short story [[The Last Council (Short Story)|The Last Council]], [[Horus]], [[Alpharius]], and [[Jaghatai Khan]] attempt to stop [[Malcador the Sigillite]] from destroying one of the Lost Primarchs' statues outside the [[Imperial Palace]]. This Lost Primarch's actions had led to his "fall" and disgrace during the [[Great Crusade]], and because of this, Malcador claimed he was no longer worthy of having a statue that bore his face. Horus and his brothers disagreed and stated that the Lost Primarch deserved to be remembered for the glory he had earned the Imperium. Horus then claimed that Malcador had overstepped his authority and was trying to amend the Imperium's early history, so that future generations would never know of the Lost Primarch. Despite their arguments, Malcador refused to listen, and angrily used his psychic powers to attack Horus, who began to utter the name of the Lost Primarch. While being psychically strangled by Malcador, Horus attempted to speak, but only managed to say "M..Mal...al". While, it is unknown if this is the name of the Lost Primarch, or if Horus was just trying to say Malcador's name, the former is more likely as Malchador felt an "He felt the old, familiar rage" start to surface within him upon hearing Horus speak that name, and Horus never stopped his attempt to defy Malcador.{{Fn|40}}

In the pre-[[Horus Heresy]] [[Horus Heresy: The Primarchs|Primarch series]] novel [[Angron: Slave of Nuceria (Novel)|Angron: Slave of Nuceria]], [[Lhorke]], a former [[Legion Master]] of the [[World Eaters]] who's now entombed in a [[Contemptor Dreadnought]], states that two [[Primarch]]s had been purged by the [[Emperor]], alongside all [[Space Marines]] who had followed them. He goes on suggesting to [[Angron]] that if the World Eaters rebel , they may share the same fate of the two unknown legions.{{Fn|43}}