Magneric was a Marshal of the Black Templars in M32. A follower of Sigismund and hero of the Horus Heresy, Magneric was badly injured in fighting against his old friend Warsmith Kalkator and subsequently interred into a Dreadnought. Magneric rarely went into the mandated sleep cycles of Dreadnoughts, becoming emotionally unstable and prone to a fanaticism unusual even for the Templars. His temperaments were usually moderated by his trusted Castellan, Ralstan. He led the Kalkator Crusade with a brutal zeal, determined to exact his vengeance on the Iron Warriors Warsmith.
Ultimately, Magneric cornered Kalkator on Dzelenic IV but both his and the Iron Warriors forces were under attack from Orks of The Beast. Facing mutual annihilation, Magneric initially refused Kalkator's calls for a temporary truce but was swayed by Ralstan. Magneric and Kalkator put aside their vendetta for a time in order to battle the Greenskins.
Magneric met his end in the Battle of Vandis, during the War of the Beast. The orks boarded Obsidian Sky in numbers and Magneric defended the bridge, killing many before he ordered the ship on a ramming course into a nearby ork carrier.