Ahem, this is the part where all the other soldiers are supposed to raise their banners and go "ZURREEEGAAAAATTTHH!", cuz that's really loud. If Durgo was the only one yelling, it'd be kinda silly.
Does Durgo know how the Castle gates are operated? Or at least how to open them? Probably Vespazian would know much better, but Durgo has an idea to use the gargoyles to transport a team over the walls who could try to open the gates from the inside and let the rest of the forces in.
While that happens, he would lead a small group to the Ash Vents. Is that workable?