The despoiler is a cretin, yet he is a cretin that galvanises the likes of you and your obsolete kin. He has failure after failure and has accomplished nothing of note.
As for my lord blackheart, a fortress monastery lies in ruin already, ashes in our wake, Villamus is a dying world. Blackheart has the fealty of more Astartes than any other, but he knows nothing but success, but only a fool strikes only because they can, a wise warrior awaits the right moment, the moment when most damage can be inflicted. That is why the Despoiler fails, and why we stay our hand, we already have the capcity to strike and strike repeatedly, but when we do it will tear the throat out, not bruise the body.
You and your kind are broken sorceror, accept this fact.