Willow said the words to this spell and released a bolt of electricity to strike her target. This spell had varying amounts of power and it did not affect all creatures targeted with this spell. At the same time, this spell could be cast non-verbally.
Willow cast this spell against the Hyberrax and its mother to defend herself, though it did little to them as their skin was invulnerable against magic. However, during her time in Quor'toth, she cast a similar spell that was able to strike and eliminate one of the creatures that tried to attack her and her companions.