Frost's hands froze in place when he heard Findlay mention that a ronso was lost in battle. That was the first C-rank monster to die among his forces, a serious blow- the ice revenant was just in a state of depleted energy and would be back in the fight after another couple days of rest, so it didn't count.
"That's not good. How did he die?" Frost asked with a pronounced frown. The ronsos were quite important to him given his direct involvement in their species establishment. Losing one of them struck a cord in his heart, filling him with a sense of loss and anger.
Findlay let out a sigh before explaining what happened. He knew his master would feel dejected at hearing the loss of one of the ronsos, so he explained in detail.