Asmasael is a Librarian of the Blood Angels Chapter. During the Diamor Campaign, he worked closely alongside Captain Aphael in fighting the Black Legion, Crimson Slaughter, Butcherhorde, and Word Bearers. However after the Chaos Lord Xorphas completed his ritual with the Banshee Stone on Amethal, Asmasael sent a distress call to Titan to request aid from the Grey Knights. In the aftermath of the ritual's completion, Asmasael managed to destroy the source of the Chaos disturbance - the Banshee Stone - and stopped the appearance of a Warp Rift on Amethal, though only for some time. During the Thirteenth Black Crusade, he was still on Amethal, guarding the site where the Chaos ritual took place, when Daemonic incursions struck the worlds of the Diamor System. As Amethal began to be overrun, the Librarian sent a desperate message to Baal asking for more reinforcements, but was denied as the Baal System was now threatened by incoming Tyranid Hive Fleets. Asmasael replied that he understood and asked that the souls of the Blood Angels fighting in the Diamor System be commended to their Primarch Sanguinius, before going to defend Amethal. He received multiple messages afterwards telling him to abandon Amethal, with whatever resources he could recover, and return to Baal immediately, but Asmasael does not or can not reply to them.
- 1: Black Crusade: Angel's Blade Chapter 3
- 2: Black Crusade: Traitor's Hate, pg. 101
- 3: Gathering Storm: Rise of the Primarch, Chapter 1: Revelation and Rebirth - Addenda Inquisitoria (Harbinger Tragedium)