The slap from the chaotic monstrosity's hands was enough to turn the ice that Walker had shot in to shards. But they also seemed to be melting at a faster rate because of the chaotic mana that had been infused in the slap.
This wasn't the only attack though. He had shot more spears of ice to see what else the chaotic monstrosity could do. He wasn't trying to immediately defeat it, but force its attention away from the demon lord that it was consuming.
Halting its growth and even destroying it would be the overall goal. However, he fount hat the demon lord's body was still lashing out with chaotic mana being sent in slashes and even small balls at the group. Gil's arrow had changed form just firing at the demon lord. But to defend against these attacks.
Creation is hard, cheer me up!