I'd get the fourth sword, then I'd take a regular dagger, and cut open a pregnant cow or cat or dog or something. I'd then slay all the kittens or calves or puppies with my new sword. Since the animals are not born yet, they would have an age of less than 0. When we add their negative age to mine, I'd become weeks or even months younger per kill! With this I will have everlasting youth!