Archmage

Wizard, Sorcerer, or Warlock Level 16

Background
Your lifelong perusal of grimoires, librams, tomes, and spellbooks has finally revealed the foundation of reality to you: Spells are each tiny portions of a larger arcane truth. Every spell is part of some far superior working, evoking just a minuscule fraction of that ultimate formula. As you continue your studies, you advance your mastery of spells so much that they begin to infuse your flesh, granting you a facility in their use undreamed of by lesser practitioners.
  You are often called to use your knowledge to defend the world from supernormal threats. Seeking ever greater enlightenment and the magical power that accompanies it, you are at times tempted by questionable relics, morally suspect spells, and ancient artifacts. Your destiny remains yours to choose—will you be archmage or archfiend?   Epic Destiny
This feature can be taken twice, with additional effects being granted on the second time it is taken.   First Level Features
Arcane Spirit: Once per day, when you die, you can detach your spirit from your body. In arcane spirit form, you heal to maximum hit points and gain the insubstantial and phasing qualities. You can cast spells up to Level 6 while in arcane spirit form, but you can’t activate magic items, or perform rituals. If you die in arcane spirit form, you’re dead. After a short rest, your arcane spirit rejoins your body, if your body is still present. Your current hit point total is unchanged, but you no longer experience the other benefits and drawbacks of being in arcane spirit form. If your body is missing, you will need other magic to return to life, but can continue adventuring in arcane spirit form if you like.   Second Level Features
Master of Spells: After taking a long rest, choose one among the levels of Wizard spells you know. Until your next long rest, the number of spell slots at that level is doubled.   Immortality
When you complete your final quest, you retreat from the world to give your full time and attention to the study of the ultimate arcane formula, the Demispell, whose hyperplanar existence encompasses all the lesser spells there ever were or ever will be. To aid your study, you build a sanctum sanctorum. At your option, your retreat provides you complete seclusion, and thus could take the form of a tower lost somewhere in the Elemental Chaos. However, you might desire to retain a tie to the world, and thus build a sanctum with a connection to the world. In such a case, you might found a new order of mages for which you serve as the rarely seen High Wizard. Alternatively, you might found a school of magic, for which you serve as the rarely seen headmaster. Regardless of your retreat’s physical form or temporal connection, your contemplation of the arcanosphere persists. As the years flow onward, your study of the fundamental, deep structure of the cosmos removes you from the normal flow of time. Eventually your material shell fades as you merge into the Demispell itself. Thereafter, your name becomes tied to powerful spells and rituals used by lesser wizards.