Iadkuzi

Iadkuzi (High Sith for 'invigoration') was a Sith alchemy practice that resulted in a slight increase in the practitioners' lifespans. The knowledge of the ritual was very rare, having only been known in ancient times by Freedon Nadd and subsequently a small number of Naddist Dark Jedi. The ritual was later discovered by an agent of Darth Plagueis, who learned the ritual and passed on knowledge of it to his apprentice, Darth Sidious. As such, Darth Tyranus also eventually learned the arts of Iadkuzi, which enabled the Count to life to slightly over a century while appearing almost half as old. Dark Side aging, the process in which a powerful Dark Side user began to appear physically and mentally frail, often counteracted the benefits of Iadkuzi, which is why neither Plagueis nor Sidious were able to maintain a younger appearance, as their strength in the Dark Side was simply too powerful for them to stave off its deteriorating properties.