It looked like the advance of the Arbites and the Astartes was short lived, and it soon turned into a running retreat when the Soritas claimed that an Emperor-bleeding Earth-Shaker cannon was aiming at their position. He didn't outwardly panic, or even inwardly panic. But Herold knew when to back the fuck up and find cover, so he did. 

He slipped the shield onto his back and turned to run, Orkish bullets scraping the rockrete and one or two even ricocheted off his shield. Orks weren't the best of shooters however, as most know. Once Adrianne dealt with the big one, a lot of the fight went out of the others as well. It probably kept him from getting a bullet in the legs. 

Herold weathered the intense barrage, almost in awe at the power the Imperium and the Emperor could wrought upon its enemies. He'd seen many engines of war, but he supposed he didn't expect the sheer white of the first explosion, and the silence that followed once the barrage was over with. 

He said nothing, bolstered by the display of the shredded ground before them. "Good to go." He assured them, his shock maul vibrating to life once more.