Rejuvex

Currently Rejuvex is the only method to make yourself younger. The reason why its in high demand is that with higher age you gain a chance of having a heart attack. And dieing. On a plus note, there's an achievement for reaching age 100!

The ingredients for this are hard to find and you are very unlikely to find this or the recipe for sale. And if you take Fibrocartilage then Rejuvex is nearly worthless to you.