Lord Mephiston is the Chief Librarian of the Blood Angels.Formerly known as Brother Calistarius,he was buried under the rubble,on Armageddon.For a long period of time,he was in the thrall of the Black Rage,wrestling with it.But Calistarius' will stayed strong,and he emerged from the rubble as Mephiston,The "Lord Of Death".Under Commander Dante he became the Chief Librarian of the Blood Angles,and his right hand man.He is one of only three known survivors of the Black Rage.
The Reborn Angel
After Gallio and Vode were both killed by Arkio's loyalists,Mephiston decided that he,instead of Dante should go and deal with Arkio.This was based on the reason that since Mephiston was a psyker,he can detect the taint.Touching down on the Blood Angels shrine-world,Sabien,Mephiston found Arkio and searched him for any taint,which he found.After that,he was about to challenge Arkio to a duel when Rafen called out and said that he will fight him.Mephiston looked into Rafen's mind and saw that Rafen had seen a vision of Sanguinius,knowing that he was destined to fight Arkio.After Rafen wounded Arkio and Arkio fled,the corrupted Inquisitor Steleordered the loyalist Blood Angels and the warriors of the Reborn to attack Mephiston and his entourage.After Rafen had defeated the princeling daemon Malfallax,Mephiston's iron will had snapped,and he fell into the Black Rage.Rafen directed the power of the Spear of Telesto at Mephiston himself to break the curse.