I was tasked to find several kinds plants. I remember vaguely the number 25 or 26, which I believe were the amount of kinds of plants I had already collected, out of a much larger (150?) amount. I was surprised to see that these plants weren't like anyone would really expect them to look like - they were actually dark green balls of a soft, moss-like substance. When I touched them, they would burst and release thousands of spores. I somehow knew that I would always breathe in several spores, while others would be scattered in the atmosphere. The ones that would get inside me would make me immune to specific diseases, and the ones in the atmosphere would decrease the incidence of those diseases on other people. Ultimately, "collecting" all kinds would make me immune to disease, as well as make the world a healthier place for all. It was implied that each kind of spore ball could be found repeatedly, so in any case, others could become immune like that.