The Long Watch.

Sabriel Ixaen of the Dark Angels successor Chapter 'The Brotherhood of Absolution' remains as the highest ranking members of his Chapter once it is nearly wiped out against an unknown threat due to him being a part of the Deathwatch. The Chaplain Mordocai of the Dark Angels gives him his task, accept the Rubicon Primaris, become Chapter Master of the Brotherhood of Absolution and lead her flagship Glory-Sunder to the world only known as XX-14 in the far western Segmentum of the Galaxy. He is to do all this while rebuilding his Chapter and without the aid of any other Chapter. Sabriel, while reluctant, accepts this honour and leaves the Deathwatch behind him to leas the crusade.