Who Killed the Warmaster Horus in Warhammer 40,000 Lore?

As a passionate 40k lore expert and gaming content creator, one of the most pivotal events in the dark future of Warhammer 40,000 is the death of Horus Lupercal – the Warmaster who led half the Space Marine legions in treachery against the God-Emperor. This act sparked the cataclysmic civil war known as the Horus Heresy. But who ultimately defeated this mighty Chaos champion?

The Emperor Was Forced to Kill His Most Beloved Son

Horus was not always the treacherous Warmaster who tried to usurp the Golden Throne. He was once the Emperor‘s most favored son, leading the glorious Great Crusade to reunite humanity. But the sinister powers of Chaos corrupted and twisted him until he turned against his father, nearly destroying everything they built.

According to the lore, it was the Emperor himself who killed Horus aboard his battle barge Vengeful Spirit above Terra – the same man who had loved him and gifted him command of his legions. After Horus delivered a mortal blow that crippled the Emperor, a lone Adeptus Custodes named Ollanius Pius attacked the Warmaster, distracting him. This gave the Emperor an opening to unleash his full psychic might, obliterating Horus‘s corrupted soul.

This was a soul-crushing moment for the Master of Mankind – he wept as he watched his greatest son die by his hand. But Chaos had left him no choice, if he did not act, Horus would have killed him and doom would have befallen mankind.

Chaos Powered Horus to Nearly Defeat the Emperor

As the Warmaster of the Great Crusade, Horus was already an unmatched military genius and strategist – his powers further enhanced by chaos to elevate him to demigod tier. At the height of his powers, empowered by all four chaos gods, many experts agree Horus could have defeated the Emperor in personal combat.

So how was his father able to emerge triumphant? The Emperor held back, hoping to save his son rather than unleash his full might. But once mortally wounded, the Emperor realized Horus was utterly lost and accepted what he must do. He tapped into his full psyker potential granted by the Golden Throne, attacking Horus with a potent psychic barrage that obliterated his soul.

Some speculate that the Emperor could not have killed Horus if he also had to focus on holding back the encroaching warp storm. Perhaps if circumstances were different, Horus would have won the day. But thankfully, due to Ollanius Pius‘s bravery, this dark ending never came to pass.

The Fall of the Warmaster Sparked the Long War

With the death of their champion, the morale of Horus‘s traitor legions crumbled, and they retreated from Terra into the Eye of Terror. There, the humility of defeat stoked their hatred and resentment as they split into warring chaos warbands. Though routed, they were determined to continue their long war against the Corpse Emperor.

10,000 years later, the Warmaster may be dead, but Abaddon the Despoiler and the Black Legion carry on Horus‘s torch. The spark of rebellion that Horus ignited with his heresy all those millennia ago has led to endless turmoil and suffering for mankind – his actions echoing through history forevermore.