Notching an arrow, Walker aimed at the immortal king who had just called out many of his shedding lizard man undead. Walker knew very well that using a greater strength arrow would result in them losing a few layers of their undead skeleton protection. The best bet was to really do more damage than that.
Hit all of them with an attack that would crush their abilities to attack and defend. Naturally, this would be tough to do with just earth, water, or fire. However, using wind? That made things a little easier. Especially since they were technically still in the light elemental plane, even with the small poison elemental plane crashing in to it.
The light mana could easily be drawn in, just as Walker sensed Su using it to her advantage, he would use it too. Especially pairing it with the wind elemental arrow he had taken from his high spatial storage.