He commanded the assault force of the Loyalist elements of the World Eaters during the Istvaan III Atrocity and met his end at the hands of his traitorous former brothers who were led by the XII Legion's Primarch Angron himself.
When the Warmaster Horus first fell to the Ruinous Powers, he knew that in order to successfully launch an all-out war against the Emperor of Mankind, he first had to remove the Loyalist elements that remained in his, as well as his other traitorous brother Primarchs' individual Astartes Legions. In order to accomplish this, he used a stirring insurrection on the formerly Compliant world of Istvaan III to accomplish his goal.
He ordered elements of the Sons of Horus, Death Guard, Emperor's Children and World Eaters Legions to deploy to Istvaan III in order to suppress the revolt being instigated by the Renegade Planetary Governor Vardus Praal. Captain Ehrlen led a division of World Eaters Loyalists towards the Precentor's Palace in Istvaan III's planetary capital, the Choral City, meeting thousands of civilians who tried to stop them. He, along with his fellow World Eaters, slaughtered all of them.
Ehrlen later encountered the Emperor's Children Captain Saul Tarvitz, who warned Ehrlen that he and his World Eaters needed to take immediate cover at the bunker complexes to the west of the Choral City, as Horus was about to virus-bomb the planet. However, Tarvitz's warning came too late, as many World Eaters were too far away from the safety of nearby bunkers or other air-tight shelters and were unable to survive the massive bombardment by biological weapons.
Assault of the Red Angel
After the planet's organic life was destroyed by the "Life-Eater" virus within the bombs, and the remains cleansed by the ensuing global firestorm, Tarvitz revealed to Ehrlen that he and his World Eaters, along with his fellow Astartes on the surface, had all been betrayed by both Horus and Angron, as well as their traitorous brother Primarchs Fulgrim and Mortarion.
Soon after, dozens of Traitor World Eaters gunships, led by Angron, descended upon Choral City, firing upon their former comrades. The gunships landed, the Traitors disembarked and fought hand-to-hand against their Loyalist former brothers, seeking to grant them an honourable warrior's death.
Captain Ehrlen led the World Eaters' counterattack on the forces of Angron and their Traitor Battle-Brothers, where he is believed to have died a grisly death at the hands of his former brethren -- his face was ripped off, and then his body was quartered by the hacking blades of several Traitors.
However, at the end of the fight, a few World Eaters managed to survive and link up with the other remaining Loyalist forces on the planet, where they helped drag out the battle against the Traitor forces for a further three solar months before Horus finally lost patience and unleashed an orbital bombardment that ended all Loyalist resistance.
During his time in service, Ehrlen suffered several serious wounds to his body, while his face was disfigured by burns.
In spite of what can only be called his sullen and brutal character, typical of Astartes of the XII Legion, he was a competent and loyal officer of the Imperium and servant to the Emperor, a trait which saw him betrayed unto death on Istvaan III.
- Galaxy in Flames (Novel) by Ben Counter
- Horus Heresy: Legions (TCG) - World Eaters Card List (Image)