In his mortal life his name was Prince Tarsem of Helstone also known as the Tarsem the Ox or Tarsem of the Fourth Circle. 
His father was Tarsig and in his youth, Neferata had pitched him and Mannfred von Carstein against each, resulting in a hours long duel in his fathers palace as he sought to stop the vampire from killing his father. Before he reached thirty years of age, Tarsem had gathered many heroes to him, defended Helstone, slain wyrms and Daemons drawing the speculative attention of three of the Mortarchs, Arkhan, Mannfred and Neferata, each of whom recognised his promise. [4a]
Defending the city from the forces of Chaos alongside hero's such as Mannfred von Carstein he was slain by the Bloodthirster Khar'zak'ghul but his soul was claimed by Sigmar to be reforged as a Stormcast Eternal.
The Bull-Hearts and eight other chambers were dispatched to the Realm of Shyish, each to search for one of the Nine Gates which would provide a way into the underworld of Stygxx and an audience with Nagash. 
In his search he found and freed Mannfred von Carstein who had been defeated and imprisoned by Taka Woebringer, an Exalted Deathbringer. Once the champion of Khorne had in turn suffered defeat, the vampire pledged to aid Tarsus in his quest. 
Their quest then brought them to the ruins of Helstone to find an artefact that would lead them to one of the nine gates. There they met the remnants of the population of Helstone, now turned into ghouls who were commanded by Mannfred to find the artefact. While in the city Tarsus faced flashbacks to his last life as Tarsem and memories of the city before its fall. The Stormcasts were then ambushed by a force Nurgle worshipping beastmen and Rotbringers who inflicted heavy casualties on the Stormcasts while Mannfred disappeared leading them to think that he was betrayed them. However Mannfred returned with a larger army of ghouls after using the Stormcasts to distract Chaos forces to recover the artefact and helped wipe out the enemies by resurrecting the skeletons of the lords of Helstone as Deathrattle while Tarsus defeated the beastmen sorcerer leading Chaos forces. 
|Stand fast, Bull-Hearts. We have won a short reprieve, but they come again, in strength. Judicators, thin their ranks. Fall back when they reach the gaps. It’ll be close work then. Hammer and shield work, eh, my friends? Who will be Triumphant? …….Only the faithful. Stand Fast, and fight as if Sigmar himself were watching. Or as if Ramus were watching, for he’s closer.
- 1: The Prisoner of the Black Sun
- 2: Soul Wars (novel), Chapter Thirteen
- 3: The Realmgate Wars: The Lords of Helstone
- 4: Hallowed Knights: Black Pyramid (novel)
- 4a: Chapter Seventeen, pg. 312