Why did Luther betray lion?

After attempting to utilize the Chaos Cultists own powers to his benefit, Luther seceded from the Imperium, claiming the Lion had betrayed them by leaving them on Caliban while the Great Crusade continued. Luther took to reading the books of a destroyed knightly order who had studied the Warp.

What Primarchs are dead?

For sure, we only know of 4 dead Primarchs.

Ferrus Manus: Slain by Fulgrim at the Drop Site Massacre on Istvann V.
Sanguinius: Slain by Horus at the Battle of Terra.
Horus: Slain by the Emperor at the Battle of Terra.
Alpharius: Slain by Rogal Dorn at the Battle of Pluto.

Is Alpharius dead?

alpharius is dead. it was in the praetorian of dorn book where he was killed. it was omegon replacing alpharius at the end. as for whether or not guilliman killed omegon that is still up to debate but it is more likely than not that omegon was killed at the great scouring that followed the horus heresy.

How did Alpharius die?

Both primarchs met in combat and Alpharius was killed. Believing the combat over, for what Astartes Legion could ever survive the loss of their primarch in battle, the Ultramarines were taken by surprise by the remaining elements of the Alpha Legion, when they struck back a solar day later.

Did Rogal Dorn kill Alpharius?

Finally, Dorn finished off Alpharius with a deadly chop of his mighty Chainsword into the top of his brother’s skull. With the death of their Primarch, the Alpha Legion fleet withdrew and retreated from Pluto. At the moment of his twin-Primarch’s death, Omegon sensed the demise of his sibling and became distant.

Is Alpha Legion traitor?

Ostensibly, the Alpha Legion are traitors – they assisted Horus in the Dropsite Massacre, did his bidding in the shadow wars of the Heresy and sieged Terra with him. John was sent to recruit the Alpha Legion for the purposes of the Cabal.