Brother Kaerell was far too occupied with ensuring that all the Xenos were sufficiently slain (which in his mind meant that none of them had heads remaining) when the vox communications from both ally and enemy came streaming in. 

Removing his black Mark Six helmet for a brief period of time, he more or less allowed his facial expressions to speak for himself during the Chaos Lord's speech... There were not many emotions, just varying states of murderous rage. However, he maintained his composure rather well, if anything he seemed almost pleased to hear that yet more foes of the Imperium were baying to have their blood spilled.

Finishing his grisly work of removing the heads from the aliens, he threw the remains into a ditch which was a short walk away, given the power-armoured strength of an Astartes he managed to drag all the bodies in a single trip. He returned chuckling to himself, a stark contrast to a previously dark and brooding exterior. With an oddly, happy tone, he spoke.

“Come now, brothers, unwillingness to fight in the Emperor's name is the first step on the path to damnation, no matter what misconceived logic is placed behind it. We have a duty to do and we shall do it, no matter what this damnable world wishes to throw at us. We are Space Marines, the sword of the Emperor, think of this execution as if the very fate of the system was placed upon our shoulders. That should be ample inspiration enough to make you want to fight....” His voice becomes rather venomous towards the end as his gene-seed mutations become readily apparent once more as his voice slipped into a horrific, yet darkly inspiring, booming sound that seemed to fill the very forest with his words.

Grabbing his chain sword, which had until now been hanging from the chest of the Kroot chieftain, Fellwalker gave the bladed teeth a quick brush over with a soft cloth before raising it high. “Onwards brothers!”