Rumored to be achievable only by the most dedicated and powerful mages, Ascension is the process of translating the very soul and being of a mage into the Supernal Realms. To most archmages, this is achieved by unlocking the Final Key of the Golden Road and allowing the archmage's essence to become pure Truth. An Ascended mage is ultimately and by all means immortal, as he effectively exists as a symbol, although he may apparently be cast out by other Ascended beings through extremely secretive and powerful means.
The Exarchs achieved Ascension through a short-cut via the Celestial Ladder and now oppose the Ascension of any other mage as a means to be the sole rulers of the Fallen World. But even they allow a truly loyal and tested Seer among them, granting Ascension as a final reward to their most loyal Ministers and Tetrarchs. Aswadim archmasters say the Abyss also offers Ascension (or a similar thing) by severing a mage completely from the Truth and granting him one of the splintered half-realities of the realm to rule over. Some rumors also claim that the final attainment of a Legacy, symbolizing the final completation of the soul, grants Ascension.