"And thus did Brother Calistarius come to Hades Hive to do war against the enemies of the Imperium that had fallen upon the planet Armageddon and there did he become a victim of the Black Rage. And he went before his Chaplain and was inducted into the Death Company, as is our way, and on the morning did take part in a grand assault upon a fortress held by the enemies of the Imperium. But as he fought against the hosts, such was the fury of the battle that the very walls of the fortress did crumble and collapse and Brother Calistarius was buried deep beneath the rubble.
"For fully seven days and seven nights did he lie there trapped, caught between death and the madness of the Red Thirst. But he did not succumb to the Red Thirst, for a vision of beloved Sanguinus came to him and told him that he must resist. And further did the vision say that he must resist not just for himself, but for us all, for should he resist then he would show us that the Red Thirst can be conquered. And so he fought the feelings of rage and the desire for blood and he defeated them and on the seventh night at the hour of midnight did he burst free from his rocky tomb, reborn as Mephiston, our Lord of Death."
Book of Mephiston, verse 23