It was not that Roy was messing around, but that he wanted to give this brat Sareth this formidable destructive power.
In Roy's plan, the sealed plague power was for Sareth to save his life. If Sareth was in danger, it meant that he had encountered a powerful enemy or enemies that exceeded the number that his ability could handle. In this case, the stronger the trump card, the better, the more ferocious, the better, so that he could kill the opponent as soon as possible to save his life.
Before Roy obtained wind power, his viruses spread either through frost power, in the form of snowflakes, or through dripping blood into a water source to spread through the water source. These two methods of proliferation were kinds of contact transmission, so the efficiency was not too high. In fact, the destructive power was not much.
