Thundercloud, a skill that Saleen developed on his own. However, it was only usable in the Well of Stars. The Well of Stars gathered massive stores of water element, conjuring a massive storm cloud.
The electrical discharge in the cloud was no longer something Saleen could have easily controlled. His power of rules was lacking, and it had always been his weakness. However, the grandmaster was unable to easily escape from the Well of Stars all the same, and he would have only ended up being slowly ground to death by the power of lightning.
Accuracy did not matter in this case, as Saleen had all the time in the world.
Using the power of the godly item in an underwater city such as the Imperial City of the Abyss, there was no way he could have run out of water element. Furthermore, the electrical discharge from the workings of the water element was practically limitless.
