Ascension is the process a Human must undergo to become a Daeva. By ascending, the person gains immortality and a pair of wings which will allow them to fly. Access to the major cities of Pandaemonium and Sanctum will only be granted after ascension.
A human may only ascend if it is willed by Aion. However, some humans believe they can change their destiny and ascend through penance.
When a character reaches level 9, they should finish the Ascension quests before completing other quests as the experience will not progress past level 10. Essentially, the quest completion will advance you to level 10. Completing other quests afterwards is a better way to advance in levels, and not lose potential experience that would otherwise be lost.
At this point, a player must choose what specialized class they would like to become. The choice is not reversible, and cannot be altered once chosen.