Go to the Black Morass in the Caverns of Time and obtain 10 Essences of Infinity from Rift Lords and Rift Keepers. Bring these along with 5 Elixirs of Major Defense, 5 Elixirs of Mastery and 5 Elixirs of Major Agility to Lorokeem in Shattrath's Lower City. *WARNING!* You can only select one alchemy specialization.
I've devoted my life to perfecting my elixirs. Despite my success, I haven't been able to create an elixir of eternal life.
I think I know the reagent I'm missing. I've heard of a place called the Caverns of Time in Azeroth where intruders known as rift lords and rift keepers phase in and out of the timeline.
This intrusive time-shifting creates tears in time itself, twisting it infinitely into crystallized essences. Bring these to me along with samples of your work and I'll teach you all I know.