Wisps manifest as balls of elemental energy. They pose no threat until they zip to your position and start emitting their power in a circular radius.
Wisps are designed to keep you moving during a fight, as being caught in their blast will open Kratos up to attacks from other enemies. Fortunately, they're very easy to kill. You'll need stop their evasive movements by having Atreus shoot at them, and then you can take them out with one or two blows. Just make sure that you aim the arrows properly as to not waste your shots.
How many Wisps have you smashed into submission? Be sure to check out our full God of War Ragnarok guide for information on how to beat every enemy, and much more.