The rainwater, akin to sulfuric acid, although not lacking in lethality, had its killing power lie in its corrosiveness. In other words, as long as one did not come into contact with that rainwater, the Azure Dragon's ability would be utterly devoid of any killing power.
In this case, an 'umbrella' could indeed be considered the natural predator to the Azure Dragon's ability.
A common umbrella would certainly not be able to ward off the Azure Dragon's ability, yet no matter how corrosive the rainwater created by the Azure Dragon, it could not affect spiritual power. Therefore, though ordinary tools were incapable of blocking that rainwater, when Zhou Tian used his spiritual power to sweep the falling rainwater aside, the Azure Dragon's ability posed a much smaller threat to him.
Of course, given the effect of the Azure Dragon's ability, as long as Zhou Tian was within its affected range, he would inevitably be subject to its influence.
